Hepatocellular carcinoma (HCC) is a common malignancy worldwide, with more than 500,000 cases presenting annually (1). Although this prevalence is not mirrored in the population of the United States, the incidence of HCC continues to increase, with more than 19,000 estimated new cases expected in 2007 in the United States. Unfortunately, this disease remains highly lethal, with more than 17,000 deaths anticipated that same year (2). Chronic liver disease is the common underlying cause of HCC.

Worldwide, chronic viral hepatitis is primarily responsible for hepatic dysfunction and cirrhosis. In Western countries, other factors such as excessive, chronic alcohol consumption may have an impact on the carcinogenesis of HCC. Hepatitis B virus (HBV) is already a well-documented entity responsible for the underlying hepatic injury found in patients with HCC. Similarly, chronic infection with hepatitis C virus (HCV) has been shown to be a powerful etiologic element (3). Despite the international prevalence and increasing incidence within the United States, successful therapy is limited to patients with early stage disease and is typically dependent on clinical factors as well as the anatomy of the cancer. As a result, multiple staging systems for HCC have been developed. We discuss the systems that have gained wide acceptance through clinical verification.

A thorough understanding of the anatomy of the liver is necessary to assess patients as candidates for surgical resection or other local therapies. The vasculature of the liver has robust inflow with the hepatic artery, a branch of the celiac artery, and the portal vein, venous blood from the intestinal tract. Consistent nomenclature is also paramount to improve understanding among caregivers and to clarify the sometimes divergent literature.

The liver lies in the right upper quadrant of the abdomen, nestled underneath the rib cage. It is completely surrounded by a peritoneal membrane, known as Glisson capsule. This investing sheath also envelopes the portal vascular structures as they enter the liver. In contrast, hepatic veins are not covered by Glisson capsule. The liver receives a dual blood supply from both the hepatic artery and portal vein. The portal vein supplies approximately 75% of the blood supply, with the hepatic artery providing the remainder. The liver is drained predominantly by three major veins: the left, middle, and right hepatic veins. The remaining drainage occurs through several small veins that directly enter the vena cava from the posterior aspect of the liver.

For surgical approaches to hepatic tumors, it is important to recognize the variability of the extrahepatic arterial anatomy (4,5). In the majority of patients, the common hepatic artery arises from the celiac trunk giving off the gastroduodenal artery, followed by a right gastric artery. The proper hepatic artery gives rise to the cystic artery followed by the right and left hepatic arteries. However, the cystic artery frequently arises from the right hepatic artery and rarely may arise from the left hepatic artery. Anatomical variants include a replaced right hepatic artery (right hepatic artery arising off the superior mesenteric artery) and a replaced left hepatic artery (left hepatic artery arising from the left gastric artery). The importance of these variants in hepatic surgery is in recognizing their presence so as to prevent inadvertent injury. Other anatomical variants exist, including accessory vessels (a vessel that exists in conjunction with a vessel with a more standard origin) and variations in the cystic artery anatomy.

An understanding of biliary anatomy and its variations is essential to perform surgery for hepatic neoplasms successfully. The proximal right hepatic duct is largely intrahepatic, while the proximal left hepatic duct is extrahepatic and runs perpendicular to the common hepatic duct to the level of the round ligament. At the round ligament, the left hepatic duct is formed by confluence of ducts from segment IV and segments II/III. The confluence of the left and right hepatic ducts is cephalad and ventral to the portal vein bifurcation. The hepatic bile duct confluence gives rise to the common hepatic duct, the portion of the duct between the confluence and the cystic duct entrance. The common bile duct extends from the cystic duct to the ampulla of Vater. The blood supply to the extrahepatic bile duct arises from the right hepatic artery superiorly and from the gastroduodenal artery inferiorly, and runs longitudinally along its course.

One of the greatest advances in hepatic surgery is the understanding of the segmental anatomy of the liver. The Couinaud system for liver segmental nomenclature is widely accepted (6,7). The liver is divided into longitudinal planes drawn through each hepatic vein to the vena cava and a transverse plane at the level of the main portal bifurcation (Fig. 32.1). The plane of the middle hepatic vein and the primary bifurcation of the portal vein divide the liver into a right and left lobe, this runs from the inferior vena cava to the tip of the gallbladder fossa (also know as the Cantlie line or portal fissure). The secondary portal bifurcations on the right and left give rise to four sectors (also sometimes called segments or sections). The segments are then numbered clockwise in a frontal plane, beginning with the first segment, historically called the caudate lobe. On the right side, this produces the anterior and posterior sectors that are split by the plane of the right hepatic vein. The tertiary branches on the right supply four segments, two in each sector. On the left, the ascending branch gives off recurrent
branches to the medial sector (8), whereas the left lateral sector is supplied by separate branches supplying segments II and III. Segment I, the caudate lobe, receives blood supply from both the left and right portal pedicles; bile ducts from segment I also drain into the right and left hepatic ducts.

The application of surgical segmental anatomy to axial radiologic imaging (computed tomography [CT] or magnetic resonance imaging [MRI] studies) is critical in evaluating the resection potential of hepatic tumors. Reading axial studies should begin with the identification of the hepatic vein insertions into the vena cava and the plane of the portal bifurcation. Any segments cephalad to the portal vein bifurcation are VII, VIII, IVA, or II. Those caudal to the portal vein bifurcation are VI, V, IVB, and III.

Most patients with HCC present with advanced disease and thus are not candidates for curative therapy. A significant proportion of the remaining patients have coexistent, severe liver disease, including cirrhosis and chronic active hepatitis, and they may not have adequate functional hepatic reserve to tolerate hepatic resection. As a result, there are multiple clinical staging systems for HCC. These systems represent attempts to standardize the initial therapy for HCC. Selection of the most appropriate candidates for surgical resection, liver transplant, or definitive tumor ablative therapy is the ultimate goal. The most widely accepted clinical staging systems include Okuda, Barcelona Clinic Liver Cancer (BCLC), Cancer of the Liver Italian Program (CLIP), and Model for End-Stage Liver Disease (MELD).