Keywordsgallbladder, cholecystitis, cholelithiasis, dysplasia, biliary intraepithelial neoplasia, intracholecystic papillary tubular neoplasm, carcinoma
Normal gallbladder 594
Routine specimen processing 597
Congenital anomalies 597
Cholesterol gallstones 598
Pigmented gallstones 598
Clinical features and treatment 599
Hydrops and mucocele 600
Other inflammatory diseases of the gallbladder 605
Diverticular disease 605
Ischaemia and infarction 606
Non-neoplastic mucosal alterations 606
Epithelial hyperplasia 606
Papillary hyperplasia secondary to metachromatic leukodystrophy 606
Adenomyomatous ‘hyperplasia’ 606
Non-neoplastic tumour-like lesions 608
Preinvasive epithelial neoplasia (dysplasia) 610
Differential diagnosis 611
Flat, nontumoural preinvasive lesions: dysplasia and carcinoma in situ 613
Mass-forming (tumoural) intraepithelial neoplasia: intracholecystic papillary tubular neoplasms 615
Mucinous cystic neoplasms 618
Malignant neoplasms 618
Differential diagnosis 620
Other invasive carcinoma subtypes 621
Spread and metastasis of carcinoma 624
Treatment and outcome of carcinoma 624
Prognostic factors and reporting of carcinoma 624
Neuroendocrine tumours 625
Mesenchymal tumours 626
Secondary tumours 626
Other tumours 626
The foregut-derived gallbladder is a pear-shaped hollow viscus attached to the posterior visceral surface of the right lobe of the liver near the caudate lobe. The inferior aspect of the gallbladder is near the pylorus, duodenum and colonic hepatic flexure. The adult gallbladder measures on average 10 cm in length and 3–4 cm in width with a wall thickness of 1–2 mm. Its volume is usually 40–70 mL, sometimes increasing to 100 mL. The superior (hepatic) surface is adherent to the liver while the inferior (free) surface is peritonealized in continuity with the visceral peritoneum of the liver. The gallbladder has traditionally been divided into three parts: fundus, body and neck. The dilated blind end, known as the fundus, bulges out from the edge of the liver. The infundibulum is the tapered portion proximal to the neck. The neck connects into the cystic duct. Hartmann pouch, a small bulge where the neck joins the cystic duct, is thought to be a consequence of chronic inflammation. Smooth muscle bundles in the cystic duct region form the spiral valves of Heister, which help control release of bile from the gallbladder. The cystic duct usually measures 3 cm in length before its confluence with the common hepatic duct to form the common bile duct.
Arterial blood is provided by the cystic artery, which usually branches from the right hepatic artery. The gallbladder’s veins drain into the liver through the hepatic surface. Most of the gallbladder’s lymphatics drain to lymph nodes in the region of the neck and cystic duct; the remaining lymphatics drain to hepatic hilar or inferior hepatoduodenal ligament and pancreatoduodenal lymph nodes and ultimately to the celiac axis.
The gallbladder wall is composed of mucosa (surface epithelium and lamina propria), a layer of loose smooth muscle bundles (tunica muscularis), perimuscular connective tissue (subserosa or adventitia) and (on the free surface) the serosa. The gallbladder does not have a muscularis mucosae or submucosa ( Fig. 10.1 ).
The mucosa is variably folded, more so when the gallbladder is contracted. The mucosa is lined by columnar epithelial cells with pale eosinophilic cytoplasm and basally located nuclei containing inconspicuous nucleoli ( Fig. 10.2 ). The epithelial cells mainly contain acidic sulfomucins (predominantly MUC5B), contrasting with the mucin of metaplastic glands. These cells do not have the characteristic acidophilic granularity (abundance of mitochondria) characteristic of the absorptive cells of the small intestine, and compared to gastric foveolar cells, they are less mucinous. Scattered among these columnar cells are thin, slender, darker cells designated ‘pencillate’ (or ‘peg’ or ‘dark’) cells, the nature of which is unclear, differing in only a few ways enzymatically and ultrastructurally from the columnar cells ( Fig. 10.2 ). Just above and oriented parallel to the basement membrane are a few randomly dispersed, inconspicuous, oval-shaped cells sometimes referred to as ‘basal’ cells, although there is no continuous basal layer in the gallbladder mucosa. Scattered T lymphocytes may be present in the epithelium. There are no melanocytes or goblet cells in the normal gallbladder. Tubuloalveolar mucous glands (which histologically resemble pyloric metaplasia that occurs in chronic cholecystitis and cholelithiasis but differ ultrastructurally and histochemically) are present in the neck region only ( Fig. 10.3 ). Gastric and intestinal metaplasia may occur in chronically irritated gallbladders.
The lamina propria is made of loose connective tissue and normally contains a few lymphocytes, plasma cells and macrophages but no neutrophils or eosinophils. Small blood vessels, lymphatics and nerve fibres are also present.
Smooth muscle layer
In contrast to the rest of the luminal gastrointestinal (GI) tract, the gallbladder lacks both a muscularis mucosae and submucosa, which has important implications for tumour staging. The only muscular layer in the gallbladder, the tunica muscularis, is composed of loosely-arranged smooth muscle bundles that do not form well-organized layers, in contrast to the muscularis propria of the rest of the GI tract. The tunica muscularis is most prominent in the neck region. Some muscle fibres protrude upward into the lamina propria at the interface. Mucosal diverticula, called Rokitansky–Aschoff sinuses, invaginate through the muscularis in up to 40% of normal gallbladders at autopsy but are more prominent in the setting of cholecystitis. Stromal cells that express CD117, probably similar to interstitial cells of Cajal, are present within the muscle layer.
Perimuscular connective tissue and serosa
Nerves, vessels, ganglia and paraganglia reside within the variable amounts of fibroelastic and adipose tissue that compose the perimuscular connective tissue of the gallbladder. On careful inspection the perimuscular tissue has two subtle layers: a thin, denser layer adjacent to the muscularis and a looser, adipocyte-rich zone. The inner fiber-rich layer also often contains thick-walled medium-sized vessels. The interlobular connective tissue of the liver is continuous with the perimuscular connective tissue of the gallbladder along the hepatic surface. Paraganglia are usually concentrated in subserosal or perimuscular connective tissue. Ganglion cells are most concentrated in the gallbladder neck and may be in the perimuscular connective tissue as well as within the lamina propria and tunica muscularis. The perimuscular connective tissue (particularly adjacent to the liver) may contain bile ductules, known as Luschka ducts, thought to represent remnants of the embryonic hepatic primordium ( Fig. 10.4 ). They are lined by cuboidal biliary epithelium and are cuffed by fibrous tissue. They may measure up to 1–2 mm and have been reported in 10% of cholecystectomy specimens. In the setting of cholecystitis, the ducts may have a pseudoinfiltrative appearance. Luschka ducts do not communicate with the lumen or Rokitansky–Aschoff sinuses. Pericholecystic lymph nodes may contain lipogranulomas, as does any intra-abdominal lymph node above the ligamentum teres.
The columnar epithelial cells of the gallbladder stain for keratin 7 (K7) but usually not K20. These cells also express cell adhesion molecule (CAM) 5.2 and anion exchanger (AE) 1 and 3. Normal columnar epithelial cells show apical cytoplasmic staining for carcinoembryonic antigen (CEA), especially with polyclonal antibody. In contrast, carcinoma cells stain diffusely for CEA. If present, neuroendocrine cells are sparse.
The gallbladder originates from an evagination of primitive endodermal cells from the embryonic foregut, as do the liver and bile ducts. The underlying mesodermal cells appear to participate by inducing the endodermal cells. An outgrowth that buds from the ventromedial endoderm opposite the dorsal pancreatic bud near the yolk sac-foregut junction by the fourth week of fetal development eventually becomes the hepatic diverticulum as it pushes into the splanchnic mesenchyme. The liver and intrahepatic bile ducts derive from the cranial portion of the hepatic diverticulum, whereas the gallbladder and cystic duct derive from the caudal portion. The ventral pancreatic bud, which gives rise to the pancreatic head and uncinate process, develops from the hepatic diverticulum near its junction with the foregut. The common embryologic origin of the gallbladder with the pancreas and other elements of the biliary tract is reflected in many pathologies involving this organ, including the different types of neoplasms. The common bile duct (CBD) is formed by elongation and canalization of the original hepatic diverticulum. The gallbladder is recognizable as a small tubular structure by 5 weeks of gestation, when the embryo measures 5 mm. At this time, it is connected to the CBD by a short stem that will later become the cystic duct. Most of the biliary tract has canalized by the eighth week of gestation. By 15–18 weeks, the layers of the gallbladder wall are completely differentiated, and by about the third month of gestation, the fetal liver begins to secrete bile.
The gallbladder has a relatively small volume (40–70 mL) relative to the 1000 mL of bile secreted by the liver on a daily basis. To compensate for this volume disparity, gallbladder epithelial cells absorb water from bile through an osmotic gradient generated by a Na + /K + -ATPase-mediated sodium-coupled transport of chloride, allowing a larger quantity of bile constituents to be effectively stored through concentration. Bile flow into the duodenum is facilitated by contraction of smooth muscle in the gallbladder and reciprocal relaxation of the sphincter of Oddi, both stimulated by ingestion of food. Gallbladder contractions are induced by the action of cholecystokinin (CCK), a peptide hormone released by the neuroendocrine cells of the small intestine, on the CCK-A receptors of the interstitial cells of Cajal. Counterintuitively, ingestion of a fatty meal also stimulates the release of somatostatin, a hormone that inhibits gallbladder contraction, from the intestine and pancreas. In light of their simultaneous release yet opposing actions, CCK and somatostatin are thought to act as physiological ‘balances’ for each other. Bile accumulates in the CBD during fasting while the sphincter of Oddi is contracted. Once the pressure in the CBD exceeds the resting pressure of the gallbladder (~10 mm Hg), bile flows into the gallbladder.
The peribiliary mucous glands in the neck and the surface epithelial cells produce mucin, most of which is neutral, heavily sulphated, and contains a few sialic residues. The most abundant mucin in the human gallbladder is MUC5B. These mucosubstances are receiving more attention recently as their contribution to the formation of gallstones is elucidated. Gallbladder bile is sterile in most individuals, likely attributable to a combination of the antibacterial action of bile acids and cholangiocyte secretion of immunoglobulin A (IgA) and defensins.
Routine specimen processing
Gallbladders must be placed in fixative promptly to avoid bile-related epithelial autolysis. The gallbladder should be opened from the fundus to the cystic duct. Ideal routine sampling should include an en face section of the cystic duct margin and a full longitudinal section taken from the fundus to the cystic duct margin, which may be divided into shorter segments. Routine inking of the cystic duct is advisable to aid in identification when it may be distorted by a variety of pathological processes.
Lymph nodes adjacent to the cystic duct should also be sampled, if present. The bile viscosity should be noted. If stones are not easily identifiable, straining the bile may make small stones and ‘floating’ polyps more apparent. Apparent luminal debris should be noted because some neoplastic or non-neoplastic polyps are notorious for becoming detached and can be easily missed.
Greater than half of gallbladder carcinomas are clinically unsuspected and grossly inconspicuous, so any polyp or mass-forming lesion should be submitted entirely for microscopic examination. Any suspicious finding on initial sections warrants careful additional sampling. As a rule of thumb, an additional two to four blocks usually suffice if focal epithelial atypia is present in the initial sections. Higher-risk lesions such as high-grade dysplasia or hyalinizing cholecystitis, on the other hand, warrant more thorough sampling not only to exclude carcinoma but also to evaluate for grossly imperceptible muscle penetration, serosal involvement or hepatic surface involvement when a carcinoma is present. When a portion of liver is included in the resection for gallbladder carcinoma, the presence or extent of liver involvement by the tumour and the status of the hepatic resection margin should be documented. If a high-grade dysplastic lesion or superficial carcinoma (‘early gallbladder cancer’) is identified, total sampling of the organ is warranted to exclude deeper invasion because the prognosis changes dramatically (see later discussion). It is also important to document whether a tumour is located in the hepatic or peritonealized aspect of the organ.
Congenital gallbladder anomalies are uncommon and include variation in number, shape or structure and position as well as heterotopias, cysts and diverticula ( Table 10.1 ).
Gallbladder agenesis and hypoplasia are rare (0.1% incidence) and usually accompany anomalies (or absence) of the cystic duct and other extrahepatic ducts. Postinflammatory shrinkage may be difficult to distinguish from congenital hypoplasia. Children with agenesis of the gallbladder may have many other congenital abnormalities, such as polycystic kidney, cardiac defects, absence of ascending colon, imperforate anus and annular pancreas. It may be discovered in adults with symptomatic choledocholithiasis or incidentally at autopsy. Agenesis of the gallbladder may be clinically insignificant in children. However, hypoplasia may be associated with other abnormalities, such as congenital biliary atresia or cystic fibrosis. In cases of extrahepatic biliary atresia, a fibrous cord containing compressed epithelial-lined structures, wisps of smooth muscle and inflammatory cells may reside in the gallbladder fossa. The porta hepatis may appear similar. Cystic fibrosis, α1-antitrypsin deficiency and idiopathic neonatal (giant cell) hepatitis may be associated with a small gallbladder (<2–3 cm). The rare duplication and even rarer triplication of the gallbladder (classified based on cystic duct arrangement) may rarely account for recurrent acute right upper quadrant abdominal pain after cholecystectomy. Duplication occurs about the sixth week of embryogenesis if the cystic primordium splits. Depending on the completeness of the split, a gallbladder may be bifid, two separate gallbladders may share a common cystic duct, or two separate gallbladders may have separate cystic ducts connecting them to the biliary tree ( Fig. 10.5 ).
Most gallbladder diverticula form as a result of inflammation, but rare diverticula may be congenital. Congenital diverticula are distinguished from Rokitansky–Aschoff sinuses (described later) by containing all the layers of the normally developed gallbladder wall. They are thought to result from incomplete cavitation during development of the gallbladder, may occur in any part of the gallbladder, and measure up to 8 cm.
Congenital cysts may occur in the gallbladder. Fundal cysts may originate as diverticula in which luminal communication is closed off by inflammation. Grossly recognizable cysts may also be produced by dilated Luschka ducts. The so-called adenomyoma or adenomyomatous hyperplasia may also be a congenital malformative process (see later).
Gallbladders may have congenital septa, dividing the lumen into separate communicating compartments. A single, centrally located, transverse septum that causes constriction creates an hourglass gallbladder . Multiple septa that divide the gallbladder into three or more compartments create a multiseptate gallbladder. This may be associated with cholelithiasis in adulthood.
The gallbladder may be ectopic (malpositioned). Some gallbladders are attached to the liver only by a mesentery and entirely surrounded by serosa. These ‘floating’ gallbladders may undergo torsion and become infarcted or may cause constriction and hypoplasia of the left hepatic lobe. Other gallbladders are entirely situated within the liver parenchyma, predisposing to cholelithiasis and infections ; these may be difficult to excise. Left-sided gallbladders (located to the left of the falciform ligament, which may be seen in the setting of situs inversus) have a prevalence of 0.2% and have been associated with exomphalos and other digestive system anomalies. Other unusual locations for the gallbladder include above the liver and in the retroperitoneum, abdominal wall, lesser omentum or falciform ligament.
Heterotopic tissues have been reported in the gallbladder, including GI, hepatic, adrenal, pancreatic and thyroid. These should be classified as ‘heterotopia’ only when they form a mass lesion, because inflammation may lead to GI and pancreatic metaplasia. Hepatic tissue should only be regarded as heterotopic once an accessory lobe or extension from the liver has been excluded. Symptoms of acute pancreatitis and chronic cholecystitis may occur with heterotopic pancreatic tissue. Perforation and haemorrhage may occasionally be associated with ectopic gastric mucosa, which is usually of both the oxyntic and antral type. Ectopic adrenal tissue is quite rare in the gallbladder. Aside from these potential complications related to gastric and pancreatic heterotopia, other heterotopias are usually inconsequential.
Inversion of the gallbladder fundus into the body results in the phrygian cap , which is clinically insignificant as long as it is not mistaken for another lesion radiographically. Despite its relatively frequent occurrence (6%), it is seldom recognized. The gallbladder must be fixed while distended and cut longitudinally in order for the phrygian cap to be demonstrated. In some cases the fundus may become adherent to the body.
In developed countries, cholelithiasis is present in 10–20% of adults ; it is very uncommon in the paediatric population ( Table 10.2 ). It has a female predilection and is more common with advancing age, perhaps related to increased biliary cholesterol secretion. Amerindian populations of both North and South America have a very high incidence (75%) of cholesterol gallstones. These populations may harbor dominant lithogenic genes.
|Cholesterol stones||Noncholesterol stones|
|Epidemiology||Northern Europe |
North and South America
|Composition||Predominantly cholesterol monohydrate||Calcium bilirubinate phosphate and carbonate||Calcium salts |
Products of fatty acid bacterial degradation
|Associated conditions||Multiparity |
Oral contraceptive use
Rapid weight loss
|Pathogenesis||Cholesterol hypersecretion |
Bile acid hyposecretion
|Elevated levels of unconjugated bilirubin||Elevated levels of unconjugated bilirubin|
|Number||Several (rarely single large stone)||Great number||Single or few|
|Shape||Round to ovoid or faceted |
On transection: radiating crystalline palisade
|Colour||Pale yellow||Jet black||Brown-yellowish|
Cholesterol stones are formed when the bile is supersaturated with cholesterol, which may result from decreased bile acid production, increased cholesterol output in bile or both. Stone formation by cholesterol monohydrate crystals is enhanced by mucin hypersecretion and gallbladder hypomotility. Cholesterol stone formation is promoted by conditions that increase hepatic cholesterol excretion, such as oral contraceptives, pregnancy, anticholesterol medications, rapid weight loss, obesity, total parenteral nutrition (TPN) and hypertriglyceridaemia, or by conditions that induce gallbladder stasis (e.g. mechanical obstruction, neurogenic/hormonal factors). Conditions that deplete bile salts (e.g. Crohn disease) may also promote cholesterol stone formation. It is not yet clear whether there is increased risk of stone formation in diabetic patients. Alcohol consumption seems to be protective against cholelithiasis.
The degree of cholesterol content influences the gross appearance of cholesterol stones ( Fig. 10.6 A ). Ten percent of gallstones are pure cholesterol stones, which measure up to 4 cm. These are smooth, round to ovoid and yellow-white and have a laminated or crystalline cut surface. Mixed stones have lower cholesterol content and thus may be layered grey-white to black depending on the bilirubin, calcium carbonate and phosphate content. Mixed stones tend to be multiple, smaller and faceted and may have a dark core and layered cut surface. At least 80% of cholesterol stones are radiolucent because they do not contain calcium carbonate.
Worldwide (particularly in Asia), pigmented stones are the most common, resulting from parasitic infections. In the United States, less than 25% of gallstones are pigmented. Pigmented stones are composed of insoluble calcium salts which form as a result of increased unconjugated bilirubin in bile and, by definition, contain no more than 30% cholesterol. Haemolytic syndromes and severe ileal dysfunction or bypass (which increase the concentration of unconjugated bilirubin in bile) predispose to pigmented stone formation, as do parasitic and bacterial infections of the biliary tract.
Pigmented stones come in black and brown varieties. Black stones may be black or deep brown with an irregular, shiny outer surface, are difficult to crush, are small (2–5 mm) and resemble glass on fracturing ( Fig. 10.6 B ). They form most often in older individuals in sterile bile but are also the most common gallstone type in patients with chronic haemolytic anaemia, cirrhosis or sclerosing cholangitis. Many black stones (50–75%) are radiopaque secondary to calcium carbonate and calcium phosphate. Brown stones are rough, flaky and soft and may appear greasy; they are usually radiolucent ( Fig. 10.6 C ). Brown stones usually form in the context of biliary stasis and bacterial (e.g. Escherichia coli ) or parasitic (e.g. Ascaris lumbricoides, Opisthorchis sinensis ) infection. Stones are produced when free fatty acids released by bacterial phospholipases complex with calcium, and unconjugated bilirubin is formed from hydrolysis of conjugated bilirubin by β-glucuronidases.
Rarely, previously documented gallstones may disappear, presumably either secondary to spontaneous dissolution or passage through the CBD or a cholecystoenteric fistula. Some gallstones become embedded within the gallbladder wall, through Rokitansky–Aschoff sinuses or mucosal ulceration. Some gallstones are observed radiographically to float in bile when they are less dense than the bile itself (sometimes induced by fasting); these gallstones may appear to contain gas radiographically, possibly produced by bacteria.
Clinical features and treatment
Gallstones grow most rapidly during the first 2 to 3 years of their production, at a rate of about 1–2 mm per year, after which time growth subsides. Most gallstones are asymptomatic. Symptomatic patients most frequently complain of right upper quadrant pain (that may be colicky) and flatulence occurring after ingestion of fatty foods. Ultrasonography can detect not only gallstones measuring over 2 mm, but also biliary ‘sludge’. Plain abdominal radiographs detect 10–25% of gallstones.
The treatment of choice for symptomatic patients is cholecystectomy. Cholecystectomy for gallstones is also indicated in children and in patients with sickle cell disease, at high risk of developing gallbladder cancer (Native Americans), with porcelain gallbladder (hyalinizing cholecystitis) or with stones >3 cm. Rarely, less invasive therapy, such as extracorporeal shock-wave lithotripsy and oral or contact dissolution therapy, may be administered, but with limited success.
There are many possible complications of cholelithiasis. Some are covered in this section; others, including cholecystitis, hydrops/mucocele and cancer, are described in other sections.
Erosion of stones through mucosa may lead to inflammatory adhesions between organs (e.g. between gallbladder and colon or duodenum) through which gallstones may ultimately pass via fistulous tracts. Stones may pass through these fistulous tracts or through the CBD without sequelae, but they may also lead to obstruction. Various obstruction-related complications include choledocholithiasis; obstructive jaundice; pancreatitis secondary to ampullary obstruction; small intestinal obstruction, usually in the ileum resulting in ‘gallstone ileus’ ; and rarely, appendiceal or colonic obstruction. Stones that are small enough to pass through the CBD and ampulla of Vater typically do not cause obstruction at any downstream site. Stones that are large enough to cause obstruction of the intestine or colon are therefore assumed to have passed through a cholecystoenteric fistula, which may or may not remain patent until surgery. Gallbladders tend to shrink and become fibrotic and embedded in adhesions when there is a healed cholecystoenteric fistula. Rarely, obstructive jaundice may result from extrinsic compression of the CBD by a gallstone in the cystic duct or gallbladder neck (Mirizzi syndrome).
Hydrops and mucocele
Hydrops refers to gallbladder distension by clear, watery liquid, and mucocele refers to distension by mucoid material. The literature cites a 3% incidence of hydrops and mucocele (combined) among pathologically examined gallbladders, but in our experience, they occur less frequently. In adults the cause is usually cystic duct obstruction secondary to an impacted stone or less often, tumours, fibrosis, kinking of the cystic duct, cystic fibrosis or extrinsic compression from a mass, as from the liver. These conditions usually cause vomiting and a right upper quadrant abdominal mass, with or without pain and tenderness. Hydrops and mucocele may require cholecystectomy in adults because they tend not to resolve spontaneously. Hydrops in children is frequently reversible and may be caused by infections (e.g. Epstein-Barr virus [EBV], streptococcal infections, typhoid, leptospirosis, viral hepatitis) or other causes of inflammation, such as Kawasaki syndrome (mucocutaneous lymph node syndrome) and Henoch–Schönlein purpura. Congenital cystic duct abnormality should also be excluded.
Hydrops and mucocele may enlarge the gallbladder significantly; up to 2 kg in some patients. Histological findings are typically unimpressive and nonspecific. Epithelial attenuation and variable Rokitansky–Aschoff sinus formation are typically observed with sparse inflammation. In some examples of mucocele, the precipitated mucin can be seen clinging to the mucosa. The gallbladder wall is usually thin in paediatric cases because of the acute nature of the obstruction in most children. In adults, however, the gallbladder shows mural thickening, sometimes with fibrosis of the tunica muscularis and stromal muciphages, reflecting the chronic nature of the process in adults.
In Western countries, a considerable amount of morbidity can be attributed to inflammatory diseases of the gallbladder. A variety of pathological processes with differing etiologies and clinical features cause the condition called cholecystitis. Although the histological features in many cases are nonspecific, clinically relevant pathological diagnoses that suggest possible causes can be made by recognizing particular patterns of inflammation.
Rapid-onset injury to the gallbladder causes acute cholecystitis, which is defined clinically by leucocytosis combined with the persistence beyond 24 hours of the constellation of acute biliary pain, right upper quadrant tenderness, guarding and fever. Acute cholecystitis is not necessarily characterized by neutrophilic inflammation, but rather is related to ischaemia with resultant congestion, vascular leakage, oedema, fibrin deposition and epithelial denudation.
Acute calculous cholecystitis
Gallstones cause 90–95% of cases of acute cholecystitis, usually when they lodge in the neck or the cystic duct. The mucosa is then injured by a combination of static bile and ischaemia. It is thought that obstruction or stone-induced mucosal trauma causes release of mucosal phospholipases from epithelial cell lysosomes. Phospholipases hydrolyze luminal lecithins to lysolecithins, which have detergent action and are directly toxic to the mucosa and activate the inflammatory cascade. Phospholipids also damage biliary epithelium. Mucosal necrosis and mural inflammation can be induced by lysophosphatidylcholine, which is present in the bile of gallbladders with cholelithiasis. Obstruction alone is not always sufficient to cause acute cholecystitis; when the cystic duct is ligated in animal models, the gallbladder shrinks without experiencing acute cholecystitis. Superimposed ischaemic injury results from impaired venous outflow secondary to gallbladder distension and mural oedema. Acute cholecystitis usually begins as a sterile process, but about 50% of cases are eventually complicated by secondary bacterial infection, usually aerobes such as E. coli , Enterobacter , Enterococcus and Klebsiella, although anaerobes such as Clostridium , Peptostreptococcus and Bacteroides are present in 20% of cases.
The most common complication of cholelithiasis is acute calculous cholecystitis, which is the most common indication for emergent cholecystectomy. This usually occurs in the sixth or seventh decade of life, with a slight female predominance. The typical clinical presentation is right upper quadrant pain, nausea, vomiting and sometimes mild jaundice. High serum bilirubin levels are usually observed only when there is also choledocholithiasis. It has been suggested that elective cholecystectomy may be reducing the incidence of acute cholecystitis.
Acute acalculous cholecystitis
The etiology of the much less common acute acalculous cholecystitis, which accounts for 5% of cases, may be difficult to determine pathologically. Acalculous cholecystitis usually develops in the setting of severe debilitating illnesses such as burns, major trauma, multisystem organ failure, cancer, nonbiliary surgery, vasculitis and diabetes mellitus. Septicaemia from haemolytic Streptococcus , Vibrio cholerae , Clostridium or Legionella and typhoid fever are also predisposing conditions. Chemical injury from TPN, hepatic arterial chemotherapy and bone marrow transplantation have been associated with acute cholecystitis. It may also occur postpartum. In patients with acquired immunodeficiency syndrome (AIDS), specific infections (e.g. cytomegalovirus, microsporidia, cryptosporidia) may cause the clinical picture of acute cholecystitis.
Ischaemic injury, which may be related to activation of factor XII, plays an important role in the pathogenesis of acute acalculous cholecystitis. The cystic artery is the gallbladder’s sole source of arterial blood, without collaterals, which is thought to contribute to its predisposition to ischaemic injury. Gallbladder stasis, viscous bile, repeated blood transfusions and dehydration increasing pigment concentration, and lysolecithins produced by bacterial contamination may also contribute to acute acalculous cholecystitis. Levels of prostaglandin E, which increases with inflammation, are seven times the normal levels in patients with acute acalculous cholecystitis. Platelet-activating factor (PAF) may contribute to acute acalculous cholecystitis by increasing vascular permeability, promoting aggregation and degranulation of neutrophils and contributing to thrombus formation and ischaemia.
Older adults may develop acute acalculous cholecystitis, although it also accounts for a higher percentage of acute cholecystitis cases in children. Fever and hyperamylasaemia may be the only presenting symptoms of acute acalculous cholecystitis. An underlying debilitating condition may also overshadow the symptoms. Acute cholecystitis with vascular thrombosis in young patients without other medical problems should prompt consideration of cocaine-induced cholecystitis, particularly if vascular compromise affects other parts of the GI tract.
Acute calculous and acalculous cholecystitis share similar pathological findings and are discussed together. Gross findings indicating acute inflammation may include oedema and distension of the gallbladder, fibrinous serosal exudate, friability or frank gangrene ( Fig. 10.7 ). Additional findings that may be appreciated at surgery may include adhesions between the omentum and gallbladder and pericholecystic fluid collections. There may be areas of serosal haemorrhage and congested subserosal vessels. The wall may be oedematous and haemorrhagic, thickened up to 2 cm. The mucosa may be oedematous and congested, ulcerated or necrotic. In the histological preparations, acute cholecystitis is often readily recognizable on visual examination of the slides, revealing a pink thickened wall caused by oedema and congestion. In calculous cholecystitis a stone may be observed obstructing the cystic duct or gallbladder neck. Sanguineous biliary material and turbid liquid fill the lumen; although this may grossly resemble pus, the cloudy nature is actually imparted by calcium carbonate and cholesterol.
Histologically, early acute cholecystitis is manifested by mural oedema, vascular congestion, haemorrhage and fibrin deposition with mucosal erosion. Eosinophils are usually scattered throughout the oedematous wall, perhaps a response to bile contents. Neutrophils, on the other hand, may not play a role in acute cholecystitis unless there is secondary infection. When choledocholithiasis exists, intraepithelial neutrophil aggregates may be observed and typically also accompany mucosal ulcers, creating a picture that some refer to as ‘active cholecystitis’. Between the 5th and 10th days of the process, a tissue culture-like myofibroblastic proliferation accompanied by lymphocytes, eosinophils, plasma cells and pigment-laden macrophages contributes to the mural thickening ( Fig. 10.8 ). This myofibroblastic proliferation with ‘tissue culture’ appearance may be misinterpreted as a sign of chronicity, but counterintuitively, it is characteristic of acute cholecystitis. However, acute cholecystitis may also be superimposed on changes of true chronic cholecystitis. Small vessels may contain fibrin thrombi. Marked reactive epithelial atypia in acute cholecystitis may mimic dysplasia (see later). Muscular arteries may demonstrate fibrinoid necrosis; in this case, the differential diagnosis of a collagen vascular disease may be noted. Surgery becomes more difficult and risky after about 72 hours into the process, secondary to organizing fibrous adhesions.
Focal or diffuse transmural infarction may lead to perforation, which is uncommon since cholecystectomy is usually performed early. Perforations may be walled off by the omentum, resulting in abscess formation. Fistulae to other organs may form in the setting of perforation. Bile peritonitis, which is frequently fatal, may result from bile leakage through a distended gallbladder even in the absence of an identifiable perforation. True mural necrosis (not to be confused with severe mucosal ulceration) characterizes acute gangrenous cholecystitis. Secondary bacterial infection may occur. Diabetic patients are particularly at risk of acute gaseous cholecystitis or emphysematous cholecystitis (mural gas gangrene), presenting radiographically as pneumobilia, which is caused by gas-forming bacterial such as Clostridium perfringens . Gas gangrene may histologically be recognized by neutrophils, eosinophils and giant cells surrounding empty spaces.
Severe acute cholecystitis with a pus-filled lumen is classified as ‘empyema’. These cases may be missed clinically secondary to atypical presentation, and mortality is unfortunately high (15–25%). Histologically, empyema is characterized by extensive mucosal ulceration with abundant suppurative inflammation.
Clinical course and treatment
Cholecystectomy is the treatment of choice for acute cholecystitis. Perforation develops in 10% of untreated patients and peritonitis in 1%. Most untreated cases subside without complication within 7–10 days and sometimes within 24 hours. Recurrences typically occur, progressively worsening in severity until surgery is required in 25% of patients. Acute calculous cholecystitis carries an overall mortality rate of 1%; frequent underlying conditions may contribute to the considerably higher mortality in acute acalculous cholecystitis, almost 40%.
Chronic cholecystitis and variants
The vast majority of cholecystectomies are performed for chronic cholecystitis, which is the most common disease of the gallbladder. More than 90% of cases are associated with stones, and it accordingly has a female predominance, as with cholelithiasis (see Fig. 10.6 ). Chronic cholecystitis may or may not be preceded by prior attacks of acute cholecystitis, and many cases are discovered incidentally during workup for other conditions when gallstones are noted radiographically.
The number and size of stones do not correlate well with the severity of injury in chronic cholecystitis, and it is not clear whether or how much stones actually contribute to the inflammation and pain. Intermittent obstruction and changes in bile composition are thought to play a role in mucosal injury. It has been postulated that in some populations with a high incidence of chronic cholecystitis, the exuberant inflammatory responses that gallbladders mount to injury may have been beneficial and protective against parasitic biliary infections in their ancestors. Bile cultures are positive in one-third of patients (frequently growing E. coli or enterococci). Helicobacter species have been identified in some studies, although their contribution to the injury is debated. Some patients may be chronic carriers of Salmonella typhi in the gallbladder. Patients with IgA deficiency, achlorhydria or malabsorption are more likely to harbor the otherwise uncommon Giardia lamblia .
The duration and severity of chronic cholecystitis impact the pathological findings. More than 90% of chronic cholecystitis patients have gallstones. The gallbladder wall may be normal or thickened. The gallbladder may be enlarged or fibrotic and small ( Fig. 10.9 ). Prior episodes of acute cholecystitis may be suggested by serosal adhesions. The mucosa may be preserved, flattened, ulcerated or granular. Regenerative areas may appear polypoid, corresponding microscopically to clusters of glands exhibiting pyloric metaplasia admixed with fibrosis and myoid cells. Hyalinizing cholecystitis, characterized by replacement of the gallbladder wall by a homogeneous thin band of hyalinized fibrous tissue with or without calcification, is found in about 1% of cholecystectomies. Cancer is often found in cases with little or no calcification.
Histological findings in chronic cholecystitis include mural thickening, variable fibrosis and variable chronic inflammation mainly by T lymphocytes, accompanied by fewer plasma cells, eosinophils and histiocytes ( Fig. 10.10 ). Patients may experience symptoms from cholelithiasis even if the gallbladder appears microscopically unremarkable, and on the lower end of the spectrum, interpretation of subtle microscopic findings as ‘mild’ chronic cholecystitis becomes subjective. Even normal gallbladders accompanying livers used for transplantation from healthy individuals dying from trauma contain sparse lymphoid cells. The term chronic active cholecystitis is applied when neutrophils are present within the epithelium; this may be a sign of obstruction and is not considered a manifestation of acute cholecystitis, and it is often not a sign of infection either ( Fig. 10.10 , inset).
Collections of bile- and lipofuscin-laden macrophages (usually accompanied by a mild lymphocytic infiltrate) characterize cholegranulomatous cholecystitis , occurring as a response to bile penetration through the epithelium. Small vessels may show luminal obliteration. Mucosal neural proliferations may occur either in a traumatic neuroma-like pattern or in a ganglioneuroma-like pattern. The impact and indentations caused by gallstones may be seen on the mucosa. The perimuscular tissue may show elastotic changes. The epithelium may be atrophic, normal or hyperplastic. Focal or patchy ulcerations are usually signs of superimposed acute/subacute injury. Epithelial regeneration or metaplasia may be observed. Pyloric gland metaplasia, which may be the only finding in some cases of chronic cholecystitis, is frequently present. Other forms of metaplasia, which may also represent general mucosal responses to chronic injury, are discussed later.
Rokitansky-Aschoff sinuses are irregular, tubular mucosal invaginations through gaps in the tunica muscularis, analogous to diverticula of the colon ( Fig. 10.10 ). They are common in chronic cholecystitis and increase in prominence with its severity. These sinuses may contain bile or stones. When they are lined by atypical reactive epithelium (a common occurrence in chronic cholecystitis), they may mimic invasive carcinoma. Conversely, many invasive gallbladder carcinomas appear deceptively bland.
As discussed previously, a septum of adenomyomatous hyperplasia or inflamed fibrous tissue may result in the formation of hourglass gallbladder. It is as yet unclear whether adenomyomatous nodules/hyperplasia represent prominent Rokitansky–Aschoff sinuses (manifesting chronic injury) or whether they are a developmental phenomenon; we suspect the latter.
Hyalinizing cholecystitis (‘porcelain gallbladder’)
From 1% to 2% of surgically removed gallbladders show replacement of the wall by a dense homogeneous band of hyalinized fibrous tissue ( Fig. 10.11 ). This may be a manifestation of longstanding injury to the gallbladder, since patients with this finding are about a decade older than those with the usual form of chronic cholecystitis. The dense, paucicellular hyalinized fibrous tissue completely or nearly completely replaces all elements of the gallbladder wall, including the muscular elements and epithelium. It often shows artefactual clefting ( Fig. 10.11 , inset) and calcifications (frequently present but not always easy to identify). Such gallbladders with entirely calcific walls were termed ‘porcelain gallbladder’ in past literature, but it has recently been demonstrated that hyalinized gallbladders with no or minimal calcification (‘incomplete porcelain’) are the entities associated with an increased cancer risk. Because the epithelium usually is almost absent in cases of hyalinizing cholecystitis, and because carcinomas that arise in this setting can be quite subtle, any epithelium observed in completely hyalinized zones of gallbladder is concerning for carcinoma ( Fig. 10.12 ). Features that help distinguish carcinoma from reactive epithelium include glands oriented parallel to the mucosal surface, nuclear enlargement and clear cytoplasm. Carcinomas arising in hyalinizing cholecystitis are difficult to stage since the normal layers of the wall are usually not recognizable; consequently, they should all be regarded as advanced lesions (at least pT2).
Mucosal-predominant lymphoplasmacytic cholecystitis
Some cases of chronic cholecystitis show diffuse mucosal involvement by dense lymphoplasmacytic inflammation within the lamina propria that does not extend into other layers of the gallbladder wall ( Fig. 10.13 ). It has recently been demonstrated that this form of chronic cholecystitis is likely a manifestation of downstream biliary obstruction from any of a variety of causes, such as biliary, ampullary or pancreatic tumours; stones impacted in the cystic duct or CBD; or sclerosing inflammatory immune-mediated conditions. Since biliary obstruction occurs in a variety of conditions, such as ulcerative colitis, primary sclerosing cholangitis and autoimmune pancreatitis, at one point this form of cholecystitis was thought to be directly associated with these conditions, although downstream obstruction instead seems to be the common denominator for this pattern of inflammation. Some studies applied the term ‘sclerosing cholecystitis’ to cases thought to be on the spectrum of IgG4-related sclerosing disorders of the pancreatobiliary tract, as discussed later. The epithelium in primary sclerosing cholangitis-related cases may be attenuated, and peribiliary mucous gland hyperplasia may be present. Intraepithelial neutrophils and storiform fibroplasia may be observed in IgG4-related cases. Table 10.3 outlines features helpful in the differential diagnosis between mucosal-predominant lymphoplasmacytic cholecystitis and IgG4-related sclerosing cholecystitis. Mucosal hyperplasia with ectatic vessels in the superficial lamina propria tend to be observed in cases related to obstruction. Nevertheless, none of these histologic findings has proved specific for the underlying cause of the cholecystitis.
|MPLC||Downstream biliary obstruction (e.g. from tumour, stone or inflammation)||Diffuse plasma cell infiltrate in lamina propria||Less frequent IgG4-producing plasma cells|
|IgSC||Autoimmune pancreatitis type 1, other IgG4-related diseases||Plasma cells lying singly in lacunae within a band of wavy basophilic sclerosis that surrounds the epithelium||Abundant IgG4-producing plasma cells (>50/high-power field)|
IgG4-related sclerosing cholecystitis
Gallbladders accompanying pancreatoduodenectomy specimens with autoimmune pancreatitis type 1 (IgG4-related lymphoplasmacytic sclerosing pancreatitis) are frequently also inflamed. Since the sclerosing pancreatitis is often associated with distal CBD obstruction, the inflammation in the gallbladder is usually of the mucosal-predominant lymphoplasmacytic type just discussed. Sometimes, more distinctive features characteristic of those seen in IgG4-related autoimmune pancreatitis (e.g. plasma cells lying in lacunae between bands of wavy basophilic sclerosis that surround glands) are observed. A diagnosis of IgG4-related sclerosing cholecystitis may be entertained in the rare case when all these features are observed in a gallbladder of a patient without pancreatic involvement or obstruction. Careful clinical correlation is required in such cases to exclude other processes. IgG4-positive plasma cells are entirely nonspecific and are present in many inflammatory conditions, including the usual cholelithiasis-associated cholecystitis. Therefore before the diagnosis of IgG4-related sclerosing cholecystitis is made, both the morphological criteria and the presence of >50 IgG4-positive plasma cells per high-power field (hpf) in multiple fields should be met.
Patients with AIDS frequently develop acute acalculous cholecystitis, which is idiopathic in more than half of cases. The most commonly identified infectious cause is Cryptosporidium . When this is the only infectious agent, the inflammation is usually mild. Cytomegalovirus (CMV), the second most common infectious etiology, may cause ulceration as it does in the GI tract. Other infectious agents, including Mycobacterium , Candida and microsporidia ( Encephalitozoon intestinalis and Enterocytozoon bieneusi ), are occasionally present.
Scattered lymphoid follicles may be present in usual cases of chronic cholecystitis, but when prominent lymphoid follicles number at least three per centimetre (as defined by some studies), in some cases mimicking lymphoma, the term follicular cholecystitis may be employed. Less than 2% of resected gallbladders show this pattern of inflammation, and it is more common in patients in the midseventh decade of life. These lymphoid follicles are usually present within the mucosa but may occasional be present within the wall. When Rokitansky–Aschoff sinuses are present, the lymphoid follicles may surround them, forming lymph node-like structures. Follicular cholecystitis was originally described in association with typhoid fever but can also be seen in the setting of infection by gram-negative bacteria or other conditions and has not been associated with immune-based injury or obstruction. Gastritis was histologically demonstrated in one-third of patients in one study.
Eosinophils are frequently a component of the mixed inflammatory infiltrate in subacute or acute cholecystitis and are present in approximately 20% of cholecystectomy specimens. They are more abundant in ulcerations, possibly as a response to chemical injury by bile. Eosinophils are rarely the prominent inflammatory cell in chronic cholecystitis cases without ulceration (<0.7% of such cases). Since eosinophils are common and abundant in subacute cholecystitis as well, there is no uniform definition of ‘eosinophilic cholecystitis’. The cases classified under this name, defined as a predominantly eosinophilic inflammatory infiltrate in the absence of ulceration, are reported to be most common in young women with allergies. Some patients also have eosinophilic gastroenteritis. Many cases may have no known associated condition, but eosinophilic cholecystitis may also be related to drug reactions and parasitic infection. If vasculitis is present in a gallbladder with frequent eosinophils, differential diagnostic consideration should be given to granulomatous angiitis with eosinophilia (Churg–Strauss syndrome).
Abundant foamy macrophages containing cholesterol, bile, ceroid and iron are the hallmark of xanthogranulomatous cholecystitis. It frequently presents with signs of acute or chronic cholecystitis in women with cholelithiasis. Bile cultures from such patients have grown Klebsiella , E. coli and Proteus mirabilis . Mucosal ulceration or Rokitansky–Aschoff sinus rupture with bile extravasation is thought to be the cause. The xanthogranulomatous process imparts a yellow colour grossly and may result in diffuse mural thickening or have a nodular appearance with formation of masses (‘pseudotumours’) or mucosal protrusions that can occasionally be mistaken grossly or radiologically for carcinoma. The foam cells are usually accompanied by a mixture of lymphocytes, plasma cells and foreign body-type giant cells. Malakoplakia may be diagnosed in the rare cases in which Michaelis–Gutmann bodies are present definitively. Fibroblastic proliferation may predominate when the process organizes. Some reports suggest association with gallbladder carcinoma, although this is questionable. In other patients, elevated serum CA19-9 has been reported without identifiable carcinoma.
Other inflammatory diseases of the gallbladder
Gallbladder infections are usually secondary and superimposed on another process such as cholelithiasis or neoplasia and thus typically present as chronic cholecystitis. These secondary infections are most often caused by enteric bacteria, especially E. coli . The gallbladder serves as a primary site of involvement for other bacterial infections such as cholera and Salmonella . Although Salmonella does not injure the gallbladder itself, it uses the gallbladder as a reservoir during active typhoid fever and in the ‘carrier’ state. Patients with gallbladder cancer may have higher rates of Salmonella positivity. The renewed interest in the association between Salmonella and gallbladder cancer is based on epidemiological studies, leading to the speculation that the salmonellae that linger on the surface of gallstones may be an instigator for carcinogenesis. Opportunistic microorganisms (see AIDS-related cholecystitis earlier), viruses (e.g. CMV, EBV, hepatitis A) and parasites (e.g. Schistosoma , Paragonimus westermani , Ascaris lumbricoides , Giardia , amoebae) may also involve the gallbladder.
Transmural inflammation of vessels (with or without fibrinoid necrosis) without inflammation in the surrounding tissue may present clinically as acalculous cholecystitis or may be an incidental finding in a gallbladder with stones. True vasculitis is not to be confused with secondary inflammation in the setting of a diffuse inflammatory process (‘innocent bystander’ phenomenon). Vasculitis of the type characteristic of polyarteritis nodosa may be isolated to the gallbladder, or it may be a manifestation of a systemic disorder such as systemic lupus erythematosus or scleroderma. Vasculitis in the setting of systemic diseases such as rheumatoid arthritis, mixed connective tissue disease, Henoch–Schönlein purpura, Churg–Strauss syndrome, Behçet syndrome or Wegener granulomatosis may also be observed in the gallbladder. Intrahepatic arterial chemotherapy has also been associated with vasculitis.
Congenital diverticula are described earlier (see Congenital anomalies ). Healing and tightening of fibrous serosal adhesions between the gallbladder and other structures may result in traction diverticula . Such fibrous serosal adhesions may result from inflammation either intrinsic to the gallbladder (e.g. from stone-induced ulcers or fistulous tracts) or extrinsic causes (e.g. prior abdominal surgery, peritonitis of any cause). The fibrous serosal adhesions and predominantly serosal-based inflammation help distinguish these from congenital diverticula in most cases.
Ischaemia and infarction
Cholecystitis is responsible for most cases of gallbladder infarction, although it may also be attributable to other causes. Thromboembolism, surgical interventions, torsion (volvulus) of the gallbladder (especially ‘floating’ gallbladder), cocaine abuse, penetrating duodenal ulcer and hypertension may all lead to gallbladder ischaemia and infarction (which may be localized or diffuse, depending on the cause). Occlusion of arterial flow to the gallbladder is usually a consequence of atherosclerosis-related thrombosis but may also result from emboli, such as from bacterial endocarditis or valvular heart disease. Either infarction or acute acalculous cholecystitis may result from venous or arterial thromboses secondary to a hypercoagulable state related to myeloproliferative syndromes. The origin of the hepatic artery may be occluded by a dissecting aneurysm extending from the coeliac artery. Impingement on arteries or veins by stones or tumours or surgical ligation may interrupt vascular flow. Grossly, the gallbladder wall may be thickened either when calculi are present or by oedema and haemorrhage. Histologically, mucosal ischaemia is manifested by at least epithelial denudation, with or without granulation tissue formation. Transmural haemorrhagic infarction is observed when the ischaemia results from venous outflow obstruction.
Non-neoplastic mucosal alterations
Lipid-laden macrophages containing cholesterol esters and triglycerides accumulate within the lamina propria and epithelium to form cholesterolosis. This is most common in adults and multiparous women and is thought to result from abnormally increased transmucosal lipid transport and supersaturated esterified cholesterol within bile. Cholesterol stones coexist with cholesterolosis in 50% of cholecystectomies and 10% of autopsy cases; formation of cholesterol stones is also promoted by supersaturated bile. Cholesterolosis is not associated with hypercholesterolaemia or coronary artery disease. It typically spares the cystic duct and may involve the gallbladder in a diffuse or patchy fashion. Cholesterol polyps may form with or without background cholesterolosis. Diffuse cholesterolosis is appreciated grossly as golden-yellow flecks in the mucosal prominences, which imparts the appearance of a ‘strawberry gallbladder’ when the intervening mucosa is congested. The luminal bile is often dark and viscid, rich in cholesterol and sometimes contains yellow particles of floating lipid termed ‘lipoidic corpuscles’.
Microscopically, cholesterolosis appears as lipid-laden macrophages filling (and often confined to) the lamina propria ( Fig. 10.14 ). Expansion of the lamina propria may impart a microvillous architecture to the mucosa. Special stains may reveal lipid accumulation within the epithelial cells as well. On occasion, deeper mural aggregates of foamy macrophages may be present. Gallbladders with cholesterolosis usually are not inflamed or involved by neoplasia, suggesting that it may induce or may be a marker of a protective environment. Also, lipid droplets might be resorbed in the setting of inflammation, preventing the development of cholesterolosis.
Exaggerated folding of otherwise normal-appearing epithelium constitutes hyperplasia in the gallbladder ( Table 10.4 ). Focal or patchy microscopic hyperplasia is frequently seen in response to injury, such as by cholesterolosis or stones. The cores of the mucosal folds may be oedematous, especially when there is downstream obstruction. The extremely unusual phenomenon in which noninflamed mucosa lined by normal epithelium with no metaplasia is thickened by tall, closely apposed, villous-like structures without nodule formation is called primary papillary hyperplasia ; it may be diffuse, segmental or focal and does not develop dysplasia. The rarity of this entity and lack of a clear definition have led some to question its existence. A complex appearance of the mucosa likely resulting from tangential sectioning superimposed on hyperplasia of otherwise normal epithelium has been called spongioid hyperplasia . Gallbladders in patients with anomalous junction of the CBD and pancreatic duct outside the duodenal wall may form atypical papillary epithelial proliferations that are probably best classified as ‘dysplasia’ or ‘intracholecystic papillary tubular neoplasms’.
|Entity||Features||Reported frequency in cholecystectomies|
|Reactive (secondary) hyperplasia||Prominent mucosal folds with epithelial cell crowding and pseudostratification||60% *|
|‘Adenomyomatous hyperplasia’ (adenomyomatous nodule)||Circumscribed intramural nodule of cystically dilated glands lined by banal columnar epithelium within fibrous stroma |
Not really hyperplastic
Rarely develop dysplasia and carcinoma
|‘Spongioid hyperplasia’||Tangential sectioning results in the appearance of fused thin mucosal folds.||10%|
|Primary papillary hyperplasia||Closely approximated, elongated papillary mucosal folds lined by bland columnar epithelium||<0.01%|
|Hyperplasia associated with a congenital disorder (AAPBD or metachromatic leukodystrophy) †||Papillary-appearing mucosal folds with occasional complex architecture |
Neoplasia may coexist.
Papillary hyperplasia secondary to metachromatic leukodystrophy
Abnormal accumulation of sulphatide within tissues characterizes the disorder metachromatic leukodystrophy ( sulfatide cholecystosis ), which results from mutation in the gene encoding arylsulphatase, responsible for degrading sulphatide (a sphingolipid, also known as 3-0-sulphogalactosylceramide). Sulphatide accumulation in the gallbladder is manifested by an increase of variably basophilic, periodic acid-Schiff (PAS)- and cresyl violet-positive macrophages within the lamina propria. The gallbladder mucosa in children with metachromatic leukodystrophy is reported to form distinctive papillary proliferations that may or may not be accompanied by intestinal metaplasia; it is unclear whether these represent dysplasia or primary or secondary hyperplasia.
The so-called adenomyomatous hyperplasia, which we prefer to call ‘adenomyomatous nodule’, may either represent a localized, distinctive type of diverticulum (probably congenital) or a malformation. Despite the name, there is no epithelial hyperplasia ( Fig. 10.15 ) (see later Non-neoplastic tumour-like lesions ).
The gallbladder epithelium may exhibit metaplasia, most frequently of the gastric type, followed by intestinal type and rarely pancreatic acinar or squamous types ( Table 10.5 ). Metaplasia is often associated with cholelithiasis, is more frequent with increasing age and may be seen anywhere within the gallbladder in a focal or diffuse fashion.
|Metaplasia type||Microscopic features||Reported frequency in cholecystectomies|
|(Pseudo)pyloric *||Columnar cells with apical pale amphophilic mucin and compressed basal nuclei lining small tubular glands (see Fig. 10.16 )||60%|
|Intestinal||Goblet cells, Paneth cells and neuroendocrine cells † among mucinous columnar cells; eosinophilic enterocyte-like cells with brush border are rare; dysplasia often coexists.||15%|
|Gastric surface (foveolar)||Tall columnar cells with abundant apical pale eosinophilic mucin and basal nuclei||5%|
|Pancreatic acinar||Small acini lined by cells with prominent nucleoli and cytoplasm that is granular and eosinophilic apically and basophilic basally||<0.01%|
|Other types ‡||Variable||<0.01%|
More than three-fourths of surgically resected gallbladders harbor the most common form of metaplasia, called pyloric metaplasia (or pseudopyloric , antral , or mucous gland metaplasia ) ( Fig. 10.16 ). Clusters of pyloric-like glands may be present in the mucosa or deeper in the tunica muscularis. Exaggerated collections of mucosal pyloric glands may give the microscopic impression of polyps or nodules. We believe most subcentimetre lesions in the literature reported as ‘pyloric gland adenoma’ actually represent florid polypoid metaplasia; to classify a polyp as ‘neoplastic’ (or adenoma), it must either display unequivocal dysplasia or form a distinct nodule >1 cm. Metaplastic pyloric glands are microscopically, histochemically and ultrastructurally distinct from peribiliary mucous glands in the gallbladder neck and cystic duct region. Some authors prefer the term ‘pseudopyloric metaplasia’, which is more accurate, because in contrast to true pyloric glands, these may express small amounts of sialo- and sulfomucins. Estrogen receptor expression has been detected immunohistochemically in some cases. Pyloric glands admixed with parietal and chief cells represent the uncommon gastric heterotopia and not metaplasia.
Sialomucin-containing goblet cells characterize intestinal metaplasia ( Fig. 10.17 ), which is much less common than pyloric gland metaplasia. In the gallbladder this is usually ‘incomplete’ intestinal metaplasia because a brush border is usually not observed on the apical aspect of the intervening columnar cells. Paneth cells may also be present. Intestinal metaplasia is present significantly more often in gallbladders with dysplasia or carcinoma and in gallbladders from regions with a high incidence of carcinoma. Additionally, goblet cells (intestinal metaplasia) are often seen in areas with epithelial atypia, and it is difficult to discern whether this atypia represents early dysplastic changes or mere atypia of the metaplastic process. Regardless, intestinal metaplasia in the gallbladder is thought to be associated with development of carcinoma (a precursor of a precursor). Convincing dysplastic epithelium also often contains goblet-like cells, which are relatively infrequently encountered in non-neoplastic cases. For these reasons, when the initial section of a gallbladder submitted for routine pathological examination reveals goblet-like cells or intestinal metaplasia, submission of an additional four blocks, each containing several tissue portions, is recommended.
About 15% of gallbladders harbor neuroendocrine cells that can be highlighted with immunohistochemical stains. Histologically, these contain fine, dull, amphophilic cytoplasmic granules located basally (in contrast to the chunkier, more eosinophilic granules located apically in Paneth cells). Most contain serotonin, whereas others express CCK, gastrin, somatostatin or pancreatic polypeptide.
The rare squamous metaplasia of the gallbladder has been noted adjacent to squamous cell carcinomas and also in hyalinizing cholecystitis (‘porcelain gallbladder’).
Pancreatic acinar cells are sometimes present in gallbladder mucosa. They most likely represent a metaplastic phenomenon rather than heterotopia, based on the absence of other pancreatic elements, as well as their size, distribution and association with other metaplasia types (especially pyloric gland type). True pancreatic heterotopia is characterized by compact, lobulated nodules that often also show islets and ducts.
Non-neoplastic tumour-like lesions
Small (mostly subcentimetre), usually inconsequential, tumour-like lesions may be produced by reactive, regenerative, inflammatory and congenital conditions in the gallbladder. These are increasingly detected radiographically with advances in technology
Polyps ( Table 10.6 )
Mucosal injury polyps
In chronic cholecystitis the mucosa may become nodular, and some of these nodules stand out from the background mucosa by transforming into broad-based polyps. Histologically, they comprise an admixture of fibrosis, myoid cells and glandular elements, thus the name ‘fibromyoglandular’ polyps ( Fig. 10.18 ). Similar polyps have previously been called ‘fibroepithelial’ or ‘fibroinflammatory’ polyps, depending on the pattern. When the stroma is more fibrous or oedematous and there is less inflammation, the term fibrous polyp has been used. These polyps are fundamentally the same, sharing glands variably distributed throughout a fibromyoid stroma, similar to prolapse-type polyps of the GI tract. Their occurrence in patients 10 years older than those with usual cholecystitis suggests that they result from longstanding injury. Fibromyoglandular polyps are usually multiple and measure less than 0.5 cm; infrequently they may measure >1 cm (<5% of cases). On one end of the spectrum, they resemble healed granulation tissue polyps, whereas in others there are more abundant pyloric glands bordering on polypoid pyloric gland metaplasia. The surface epithelium may show regenerative hyperplasia but is more frequently denuded. Dysplasia is present in about 15% of cases, usually resulting from colonization by dysplasia and carcinoma involving the background mucosa.
|Gross features||Microscopic features||Frequency|
|Injury-related polyps (mean size, 0.4 cm; commonly multiple)|
|Fibromyoglandular polyp||All types of injury-related polyps: Raised with flat round surface; may be pedunculated on a broad base; only 5% are >1 cm.||Variably shaped glands (often metaplastic) haphazardly arranged within fibrous or myoid stroma||40%|
|Polypoid pyloric gland metaplasia||Nodular clusters of small, round, pyloric-type glands||5%|
|Inflammatory (granulation tissue) polyp||Granulation tissue, inflammation, oedema||<3%|
|Fibrous (‘stromal’) polyp||Variably inflamed fibrous stroma without glands||<1%|
|Lymphoid polyp||Prominent lymphoid aggregates or follicles; may have background follicular cholecystitis||<1%|
|Cholesterol polyps (mean size, 0.5 cm; usually not multiple)|
|Pedunculated cauliflower-like or branching architecture; rarely (5%) >1 cm||Cauliflower-like architecture and stromal lipid-laden macrophages or just stromal edema; stroma mostly devoid of glands; background usually uninjured with infrequent cholesterolosis (<30%)|
|Other rare polyp types (variable sizes; usually solitary)|
|Hamartoma, inflammatory fibroid polyp, etc.||Variable||Variable||<0.1%|
Polypoid pyloric gland metaplasia
Pyloric gland metaplasia, the most common type of metaplasia in the gallbladder that develops in response to chronic mucosal injury, may form nodular protrusions. It is clear from the literature, which reports the average size of pyloric gland adenoma as 0.7–0.9 cm, that many exuberant forms of pyloric gland metaplasia are being classified as ‘pyloric gland adenoma’. We do not consider these to be neoplastic (adenomatous) unless they show unequivocal cytological dysplasia, or unless they form tight nodules that stand out from the background mucosa. We employ a size cutoff of 1 cm to classify a nodular proliferation of normal-appearing pyloric glands as ‘neoplastic’; this is also the size cutoff applied to separate mass-forming preinvasive neoplasms of the pancreas and biliary tract from earlier lesions (see later Mass-forming [tumoural] intraepithelial neoplasia: intracholecystic papillary tubular neoplasms ).
Polypoid nodules form as a result of a variety of inflammatory conditions in the gallbladder. Severe acute or subacute cholecystitis may be associated with the most common examples of inflammatory polyps, including granulation tissue polyps and polypoid xanthogranulomatous nodules in xanthogranulomatous cholecystitis. Prominent mucosal lymphoid follicles, most frequently seen in follicular cholecystitis, may protrude to form epithelial-covered lymphoid polyps .
Stromal polyps form during the organization phase of cholecystitis. As discussed earlier, ‘fibrous polyps’ are composed almost exclusively of fibrous tissue. The term ‘neurofibroma-like polyp’ has been applied to aggregates of nerve sheath cells resembling Schwann cell hamartomas of the GI tract. The precise aetiology is unclear, but they seem to be related to injury of some type and are more common in gallbladders with cholesterolosis.
Cholesterol polyps are the most common polyps to be found in otherwise uninjured gallbladders. Histologically, they are characterized by a cauliflower-like polyp pedunculated on a thin stalk with lamina propria filled with lipid-laden macrophages, appearing to be a polypoid form of cholesterolosis ( Fig. 10.19 ). They may be multiple. Surprisingly, however, the background mucosa often does not show cholesterolosis, and in 14% of cholesterol polyps themselves, stromal macrophages are undetectable, but the architecture is characteristic of cholesterol polyps. In cases without detectable macrophages, the stroma is often oedematous, presumably containing the broken-down product of macrophages. Gallbladders with cholesterol polyps usually do not have cholelithiasis or any features to suggest chronic cholecystitis. This may be interesting to note considering cholesterol polyps appear to be almost as common in men as in women, whereas most other gallbladder pathology is more common in women.
Cholesterol polyps are non-neoplastic but dysplasia (mostly low grade) has been reported in 4% of cases. Cholesterol polyp-like architecture and lipid-laden macrophages in 35% of patients suggest that the complex-tubular type of intracholecystic papillary neoplasms may arise from cholesterol polyps. Despite the neoplastic nature of the complex-tubular type of intracholecystic papillary neoplasms, invasive carcinoma almost never develops within them. Thus, cholesterol polyps are non-neoplastic and also non-precancerous for all practical purposes.
Other, rare specific polyp types
Inflammatory fibroid polyps similar to those that occur in the luminal GI tract have been reported to occur in the gallbladder on rare occasion. We have seen a case with neural features.
Patients with Peutz–Jeghers syndrome and Cowden disease may develop hamartomatous polyps, histologically showing disorganized epithelial proliferation with focal cystic areas.
Heterotopic tissue may form nodules measuring up to 2 cm in the gallbladder. Cholecystitis-like symptoms and ulcers have been associated with gastric heterotopia in children and young adults.
Perhaps the most common cysts in the gallbladder wall are formed from expansion of Rokitansky–Aschoff sinuses or adenomyomatous nodules. Microscopic cysts may also be formed by dilated Luschka ducts. One must be astute not to underinterpret the bland appearance of the tubulocystic variant of biliary adenocarcinoma, which can appear deceptively benign.
Mural nodules of cystically dilated glands within a fibromuscular stroma that occur most often in the gallbladder fundus are referred to as ‘adenomyoma’ or adenomyomatous hyperplasia (see Fig. 10.15 ). Despite the name, there is nothing really hyperplastic about these lesions, and the stroma contains minimal to no myoid component. Grossly, they form well-circumscribed grey or yellow-white, rubbery mural thickenings with trabeculations or a sieve-like arrangement on sections. They can occasionally form mucosal lumps (‘polyps’). In the rare presentation as a diffuse process, it is referred to as ‘adenomyomatosis’. Some authors suggest this may be an exuberant form of Rokitansky–Aschoff sinuses, but many features also point to a developmental nature. For example, the architecture is distinct from that of Rokitansky–Aschoff sinuses, they usually do not communicate with the lumen, and the background gallbladder often shows neither other Rokitansky–Aschoff sinuses nor signs of injury. Instead, some examples show features of duplication.
Adenomyomas may superficially mimic adenocarcinoma secondary to the deep location of their glands; this may be confounded by the occasional finding of impingement of benign glands on nerves, simulating perineural invasion. That said, in situ and invasive carcinoma may occasionally develop within adenomyomas even without such changes in the background gallbladder. In our experience, high-grade dysplasia or carcinoma is seen in <5% of adenomyomatous nodules. The term mural intraductal papillary mucinous neoplasm refers to adenomyomas containing a papillary proliferation of dysplastic epithelium.
Masses mimicking carcinoma may sometimes be formed by extensive myofibroblastic proliferation resulting from inflammatory injury. This is particularly evident in cases of xanthogranulomatous cholecystitis. Pseudotumours in the gallbladder and extrahepatic biliary tree may be observed in cases of eosinophilic cholecystitis as well. Such findings may also be present in cases of IgG4-related sclerosing disease.
The gallbladder may be involved in cases of systemic amyloidosis. As in other parts of the GI tract, the amyloid may deposit in vascular walls and the muscularis.
Preinvasive epithelial neoplasia (dysplasia)
In the gallbladder, preinvasive epithelial neoplasia may be either flat or mass forming ( Table 10.7 ). Non-mass-forming (flat) intraepithelial neoplasia (dysplasia) is usually present in gallbladders with invasive adenocarcinomas but can also be an unexpected finding in a gallbladder without a mass lesion. In the World Health Organization (WHO) classification (2010), the synonym of ‘biliary intraepithelial neoplasia’ used for bile ducts was proposed as potentially applicable for gallbladder counterparts as well, although most authors still prefer to use the term ‘dysplasia’ in the gallbladder. Mass-forming preinvasive neoplasia comprises ‘adenomas’ and ‘intracystic papillary neoplasms’. For practical purposes and simplification, we apply the term ‘intracholecystic papillary tubular neoplasm’ for both types of mass-forming preinvasive neoplasia. Flat and mass-forming preinvasive neoplasia are discussed separately later, but the following points are relevant to both.
|General category||Specific entities|
|Flat (nontumoural) dysplasia||Low-grade dysplasia (BilIN-1 or BilIN-2 per WHO, 2010)|
|High-grade dysplasia/CIS (BilIN-3 per WHO, 2010)|
|Mass-forming (tumoural) intraepithelial neoplasia: intracholecystic papillary tubular neoplasms (ICPTNs) (IPN and adenoma per WHO, 2010)||Often mixture of biliary, gastric, intestinal or oncocytoid cell types|
|Complex tubular nonmucinous type|
It is well recognized that preinvasive neoplasia in the gallbladder is a precursor to invasive carcinoma as well as an indication of carcinoma elsewhere in the biliary tract. This is based on its usual identification adjacent to invasive carcinomas, its more frequent identification in regions with a higher incidence of gallbladder carcinoma and morphological features recognizable as neoplasia analogous to that occurring in other organs. Fortunately, even high-grade dysplasia/carcinoma in situ is associated with a 90% 10-year survival, if invasive carcinoma is definitively excluded by total sampling of the gallbladder. The prognosis is less favourable when the process involves Rokitansky–Aschoff sinuses. It may take 8 to 10 years before recurrence or metastasis is detected, suggesting that these tumours may actually represent new primaries, and that the dysplasia is a marker of a ‘field effect’ in the biliary tract.
A two-tiered system (low and high grade) is employed for grading gallbladder dysplasia. The two-tiered approach is not only more practical but also more reflective of the biological behaviour, and it parallels a similar two-tiered system recently applied to pancreatic precursor lesions (about which more is known). The criteria differ in some respects from those used in the rest of the GI tract and in some cases are based on the frequency that a given pattern is associated with invasion.
Dysplasia versus reactive atypia
Marked cytological epithelial atypia may be observed in the gallbladder secondary to a variety of insults. The difficulty presented by the morphological similarities between reactive atypia and dysplasia is magnified by the close association of true dysplasia in the gallbladder with longstanding inflammation, injury and repair. Nevertheless, epithelial atypia restricted to eroded, ulcerated, haemorrhagic or acutely inflamed areas should not be overinterpreted. Evaluation of additional tissue sections (typically four additional blocks with multiple tissue portions each) has been advocated to help in the differential of low-grade dysplasia versus reactive changes. In recent international consensus studies, different patterns of reactive atypia were elucidated, as follows:
Focal epithelial atypia of healing erosion presents as patchy basophilic foci amid relatively intact mucosa ( Fig. 10.20 ). These can closely mimic dysplasia because they show crowding and stratification of nuclei and brisk mitotic activity. Characteristic findings that allow the recognition of these lesions as reactive atypia include the presence of maturation toward the surface, similar to the criteria in Barrett oesophagus, and accompanying stromal changes (either capillarization or subtle fibrosis), which in some cases form a band in the surface similar to the pattern in collagenous colitis. Often, intercellular spaces are accentuated, forming clefts, which are regarded as a sign of cell maturity and alignment. Additionally, although they form basophilic zones and nuclear molding/overlapping contributes to their densely basophilic appearance, the nuclei that are individually identifiable often show pale, uniform chromatin. Also, the nucleoli are clearly evident but are typically small and basophilic.