David E. Beck, Steven D. Wexner, Tracy L. Hull, Patricia L. Roberts, Theodore J. Saclarides, Anthony J. Senagore, Michael J. Stamos and Scott R. Steele (eds.)The ASCRS Manual of Colon and Rectal Surgery2nd ed. 201410.1007/978-1-4614-8450-9_49
© Springer Science+Business Media New York 2014
49. Miscellaneous Neoplasms
(1)
Department of Surgery, The Ottawa Hospital – General Campus, Ottawa Hospital Research Institute, 501 Smyth Road, CCW 1617, Ottawa, ON, K1H 8L6, Canada
Abstract
These tumors are based on their tissue of origin and include epithelial, mesenchymal, neural, vascular, or lymphoid tumors.
Carcinoid tumors are neuroendocrine in origin and originate from Kulchitsky cells in the crypts of Lieberkuhn, which represent a type of enterochromaffin cell.
Kulchitsky cells use various amine precursors to synthesize several hormones, neuropeptides, and neurotransmitters such as serotonin, adrenocorticotrophic hormone, bradykinin, histamine, dopamine, substance P, neurotensin, kallikrein, and prostaglandins E and F.
These tumors are based on their tissue of origin and include epithelial, mesenchymal, neural, vascular, or lymphoid tumors.
Carcinoid Tumors
Carcinoid tumors are neuroendocrine in origin and originate from Kulchitsky cells in the crypts of Lieberkuhn, which represent a type of enterochromaffin cell.
Kulchitsky cells use various amine precursors to synthesize several hormones, neuropeptides, and neurotransmitters such as serotonin, adrenocorticotrophic hormone, bradykinin, histamine, dopamine, substance P, neurotensin, kallikrein, and prostaglandins E and F.
Carcinoid tumors can develop in the bronchopulmonary system (67 %) and gastrointestinal tract (25 %).
There is a higher incidence in females (~2:1), with tumors for all patients occurring typically between the fifth and seventh decade of life.
Within the intestinal tract, carcinoids occur mostly commonly in the midgut (62 %) followed by hindgut (30 %) and foregut (7 %).
The most common site for a carcinoid tumor is within the appendix (35 %) and small intestine (23 %), usually within 2 ft of the ileocecal valve.
Rectal carcinoid tumors account for approximately 20 % of all gastrointestinal carcinoids and account for 1 % of all rectal tumors.
Synchronous carcinoid tumors occur in approximately 25 % of patients with foregut and midgut carcinoids, but are rare with hindgut tumors.
Carcinoid tumors are associated with an increased incidence (up to 50 %) of other malignant tumors that includes gastric, esophageal, colorectal, lung, prostate, and urinary tract tumors.
Pathology
Increased cellular atypia, high mitotic activity, or necrosis are suggestive of more aggressive tumors and are termed atypical/anaplastic carcinoid tumors.
Silver staining traditionally confirms carcinoid tumors as serotonin reduces silver salts to metallic silver (argentaffin positive). Tumors that uptake silver salts but cannot reduce silver unless an external reducing agent is added are termed argyrophilic.
Midgut carcinoids are mostly argentaffin positive. Hindgut carcinoids are usually mixed with 60–70 % being argyrophil and 8–16 % being argentaffin positive.
Immunohistochemistry uses antibodies that target various cytoplasmic proteins including chromogranin, synaptophysin, and neuron-specific enolase to diagnose carcinoids.
Clinical Presentation
Carcinoid syndrome, occurring in only 10–18 % of all carcinoid patients and 50 % of individuals with advanced disease, is characterized by flushing, severe abdominal pain, diarrhea, hypotension, or hypertension, and can be precipitated by severe stress including surgery, anesthesia, and adrenergic agents.
Less than 1 % will have the carcinoid syndrome as the initial clinical manifestation.
Most patients will be symptomatic for a median duration of 2 years prior to diagnosis.
Up to 90 % of symptomatic patients will have an advanced tumor often with metastasis.
Approximately 50 % of all gastrointestinal carcinoid tumors will be diagnosed following appendectomy.
Midgut carcinoid tumors present with abdominal pain in up to 40 % of individuals, while hindgut carcinoids are nonsecretory and are almost always asymptomatic and discovered incidentally by the pathologist following polypectomy.
Occasionally, larger tumors will present with bleeding, obstructive symptoms, and tenesmus.
Serotonin is responsible for abdominal cramping and intestinal hypermotility manifesting as diarrhea, and occurs in 80 % of patients with the carcinoid syndrome.
Kallikrein secretion accounts for wheezing and flushing, the latter occurring in 85 % of affected patients.
Intestinal obstruction leading to possible arterial insufficiency is due to mesenteric and retroperitoneal fibrosis.
Right-sided heart failure, due to severe damage to the tricuspid and pulmonary valves, accounts for 50 % of the deaths from the carcinoid syndrome, and correlates with higher 5-hydroxyindolacetic acid (5-HIAA) levels.
Midgut tumors are most commonly associated with the carcinoid syndrome as these tumors produce high levels of serotonin. Almost 90 % of individuals with the carcinoid syndrome will have a midgut carcinoid tumor.
Diagnostic Tests
Biochemical Tests
24-h urine 5-HIAA measurement is the most useful biochemical test for diagnosing carcinoid tumors in the symptomatic patient, with a sensitivity and specificity of 73 and 100 %, respectively.
Chromogranin A is a sensitive serum marker but is nonspecific for carcinoid tumors.
Imaging Tests
Computerized tomography (CT) scan of the thorax and abdomen/ pelvis should be performed in symptomatic patients to identify the primary tumor and extent of disease.
Somatostatin receptor scintigraphy (SRS) scan can identify occult metastasis in patients being considered for curative resection and to determine if the patient is likely to respond to octreotide.
Whole body positron emission tomography (PET) relies on differential metabolic uptake and is used increasingly for carcinoid tumors.
Esophagogastroscopy and colonoscopy should be considered in patients with metastatic disease with an unknown primary.
Electrocardiography and echocardiography should be performed in all patients to rule out right-sided valvular disease especially prior to elective surgical resection.
Treatment
Carcinoid tumors greater than 2 cm diameter are usually malignant in most locations except in the ileum, where nearly all tumors will have metastasized.
Small Bowel Carcinoids
Small bowel resection including a resection of the mesenteric lymph nodes is indicated even in patients with known metastatic disease to reduce the likelihood of developing small bowel obstruction or mesenteric fibrosis and ischemia.
The entire small intestine should be carefully examined at the time of laparotomy to exclude the possibility of a synchronous tumor.
Appendiceal Carcinoids
Appendiceal carcinoid tumors are the most common tumor of the appendix. These tumors are rarely multicentric and tumor size is the best prognostic indicator, with most tumors less than 2 cm rarely metastasizing to regional lymph nodes or distally.Related posts:
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