16 Extrahepatic Bile Ducts
(Sarcomas and carcinoid tumors are not included.)
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SUMMARY OF CHANGES
• The T and N classifications have been redefined and simplified.
• Invasion of the subepithelial fibro (muscular) connective tissue is classified as T1 irrespective of muscular invasion, which cannot always be noted because of the scarcity of muscle fibers in some bile duct segments.
• T2 is defined as invasion beyond the wall of the bile duct.
• The T classification allows one to separate locally invasive tumors into resectable (T3) and unresectable (T4).
• Invasion of branches of the portal vein (right or left), hepatic artery, or liver is classified as T3.
• Invasion of the main portal vein, common hepatic artery, and/or regional organs is classified as T4.
• The stage grouping has been changed to allow Stage III to signify locally unre- sectable disease and Stage IV to indicate metastatic disease.
C24.0 Extrahepatic bile duct
C24.8 Overlapping lesion of the biliary tract
C24.9 Biliary tract, NOS
INTRODUCTION
Malignant tumors can develop anywhere along the extrahepatic bile ducts (Figure 16.1). Of these tumors, 70–80% involve the confluence of the right and left hepatic ducts (hilar carcinomas), and about 20–30% arise more distally.
Diffuse involvement of the ducts is rare, occurring in only about 2% of cases.
All malignant tumors of the extrahepatic bile ducts inevitably cause partial or complete ductal obstruction. Because the bile ducts have a small diameter, the signs and symptoms of obstruction usually occur while tumors are relatively small. Because of their invasion of major vascular structures and direct exten- sion to the liver, hilar carcinomas are more difficult to resect than those that arise distally and are associated with a worse prognosis (because of the low rate of resectability).
This TNM classification applies only to cancers arising in the extrahepatic bile ducts above the ampulla of Vater. This includes malignant tumors that develop in congenital choledochal cysts and tumors that arise in the intrapan- creatic portion of the common bile duct. Patients with advanced (metastatic) disease and a primary tumor in the intrapancreatic portion of the common bile duct may be misclassified as having pancreatic cancer if surgical resection is not performed. In such cases, it is often impossible to determine (from radiographic images or endoscopy) whether a tumor arises from the intrapancreatic portion of the bile duct, the ampulla of Vater, or the pancreas. Tumors of the pancreas and ampulla of Vater are classified separately.
ANATOMY
Primary Site. Emerging from the transverse scissura of the liver are the right and left hepatic bile ducts, which join to form the common hepatic duct. The cystic duct, which connects to the gallbladder, joins the common hepatic duct to form the common bile duct, which passes posterior to the first part of the duodenum, traverses the head of the pancreas, and then enters the second part of the duodenum through the ampulla of Vater. Histologically, the bile ducts are lined by a single layer of tall, uniform columnar cells. The mucosa usually forms irregular pleats or small longitudinal folds. The walls of the bile ducts have a layer of subepithelial connective tissue and muscle fibers. It should be noted that the muscle fibers are most prominent in the distal segment of the common bile duct. More proximally, the muscle fibers are sparse or absent, and the walls of the bile ducts consist largely of fibrous tissue.
Regional Lymph Nodes. Accurate tumor staging requires that all lymph nodes that are removed be analyzed. Optimal histologic examination of a regional lymphadenectomy specimen should include analysis of a minimum of three lymph nodes. The regional lymph nodes are the same as those listed for gallbladder cancer and include the following: hilar, celiac, periduodenal, peri- pancreatic, and superior mesenteric. The hilar nodes include the lymph nodes along the common bile duct, hepatic artery, portal vein, and cystic duct.
Metastatic Sites. Extrahepatic bile duct carcinomas can extend to the liver, pancreas, ampulla of Vater, duodenum, colon, omentum, stomach, or gallblad- der. Tumors arising in the right or left hepatic ducts usually extend proximally
Left hepatic duct Right hepatic duct Common hepatic duct
Cystic duct Common bile duct (Choledochus)
Ampulla of Vater C24.1
C24.0
FIGURE 16.1. Anatomic sites of the extrahepatic bile ducts.
into the liver or distally to the common hepatic duct. Neoplasms from the cystic duct invade the gallbladder, common bile duct, or both. Carcinomas that arise in the distal segment of the common bile duct can spread to the pancreas, duo- denum, stomach, colon, or omentum. Distant metastases usually occur late in the course of the disease and are most often found in the liver, lungs, and peritoneum.
DEFINITIONS Primary Tumor (T)
TX Primary tumor cannot be assessed T0 No evidence of primary tumor Tis Carcinoma in situ
T1 Tumor confined to the bile duct histologically (Figure 16.2) T2 Tumor invades beyond the wall of the bile duct (Figure 16.3)
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T1
T1 or
Perifibromuscular connective tissue
Subepithelial connective tissue (Lamina propria)
Fibromuscular wall
FIGURE 16.2. Two views of T1: both tumors are confined to the bile duct histologically.
T2
FIGURE 16.3. T2 is defined as tumor that invades beyond the wall of the bile duct.
T3
A
FIGURE 16.4. A. T3 is defined as tumor invading the liver (as illustrated), gallbladder, pancreas, and/or ipsilateral branches of the portal vein (right or left) or hepatic artery (right or left).
T3 Tumor invades the liver, gallbladder, pancreas, and/or ipsilateral branches of the portal vein (right or left) or hepatic artery (right or left) (Figures 16.4A–C)
T4 Tumor invades any of the following: main portal vein or its branches bilat- erally, common hepatic artery, or other adjacent structures, such as the colon, stomach, duodenum, or abdominal wall (Figures 16.5A, B) Regional Lymph Nodes (N)
NX Regional lymph nodes cannot be assessed N0 No regional lymph node metastasis N1 Regional lymph node metastasis Distant Metastasis (M)
MX Distant metastasis cannot be assessed M0 No distant metastasis
M1 Distant metastasis
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T3
B
C
T3
Cystic duct
Main portal vein
Common bile duct
FIGURE 16.4. B. T3 tumor invading the pancreas. C. T3 tumor with ipsilateral invasion of the right portal vein and gallbladder.
T4
Common hepatic artery Cystic duct
Main portal vein
Common bile duct
Right and left portal vein
A
T4
Cystic duct
Duodenum
B
FIGURE 16.5. A. T4 is defined as tumor that invades any of the following: main portal vein or its branches bilaterally, common hepatic artery, or other adjacent structures, such as the colon, stomach, duodenum, or abdominal wall. Here, tumor invades the common hepatic artery and bilateral branches of the portal vein. B. T4
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STAGE GROUPING
0 Tis N0 M0
IA T1 N0 M0
IB T2 N0 M0
IIA T3 N0 M0
IIB T1 N1 M0
T2 N1 M0
T3 N1 M0
III T4 Any N M0
IV Any T Any N M1
