18 Exocrine Pancreas
(Endocrine tumors arising from the islets of Langerhans and carcinoid tumors are not included.)
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SUMMARY OF CHANGES
• The T classification reflects the distinction between potentially resectable (T3) and locally advanced (T4) primary pancreatic tumors.
• Stage grouping has been changed to allow Stage III to signify unresectable, locally advanced pancreatic cancer, while Stage IV is reserved for patients with metasta- tic disease.
C25.0 Head of pancreas C25.1 Body of pancreas C25.2 Tail of pancreas
C25.3 Pancreatic duct C25.7 Other specified parts
of pancreas
C25.8 Overlapping lesion of pancreas C25.9 Pancreas, NOS
INTRODUCTION
In the United States, pancreatic cancer is the second most common tumor of the gastrointestinal tract and the fifth leading cause of cancer-related death in adults. The disease is difficult to diagnose, especially in its early stages. Most pan- creatic cancers arise in the head of the pancreas, often causing bile duct obstruc- tion that results in clinically evident jaundice. Cancers that arise in either the body or the tail of the pancreas are insidious in their development and often far advanced when first detected. Most pancreatic cancers are adenocarcinomas, which usually originate from the pancreatic duct cells. Surgical resection remains the only potentially curative approach, although multimodality therapy that includes innovative systemic agents and often radiation therapy is available.
Staging of exocrine pancreas cancers depends on the size and extent of the primary tumor. This TNM classification does not apply to endocrine tumors.
ANATOMY
Primary Site. The pancreas is a long, coarsely lobulated gland that lies trans- versely across the posterior abdomen and extends from the duodenum to the splenic hilum. The organ is divided into a head with a small uncinate process, a neck, a body, and a tail. The anatomic subsites of the pancreas are illustrated in Figure 18.1. The anterior aspect of the body of the pancreas is in direct contact with the posterior wall of the stomach; posteriorly, the pancreas extends to the aorta, splenic vein, and left kidney.
Tumors on the head of the pancreas are those arising to the right of the superior mesenteric-portal vein confluence (Figure 18.2, posterior view of pan- creatic head). The uncinate process is part of the pancreatic head. Tumors of the body of the pancreas are roughly defined as those arising between the superior mesenteric-portal vein confluence and the aorta. Tumors of the tail of the pan- creas are those arising between the aorta and the hilum of the spleen.
Portal vein
Aorta
Tail C25.2 Body
C25.1 Head
C25.0 Superior mesenteric vein
Superior mesenteric artery Celiac axis
Common bile duct
FIGURE 18.1. Anatomic subsites of the pancreas.
FIGURE 18.2. Posterior view of pancreatic head with dotted line indicating the location of the confluence of the portal and superior mesenteric veins. The hatched area shows the uncinate process margin.
Regional Lymph Nodes. A rich lymphatic network surrounds the pancreas and accurate tumor staging requires that all lymph nodes that are removed be analyzed. Optimal histologic examination of a pancreaticoduodenectomy spec- imen should include analysis of a minimum of 10 lymph nodes, although patho- logic analysis of fewer than 10 lymph nodes may still result in a pN0 designation.
The nomenclature for the regional lymph nodes of the pancreas is not stan- dardized, but the main classification systems currently in use are descriptive and based on the anatomic location of the nodes. Accordingly, the pancreas has two broad groups of regional nodes: those that form a ring around the organ and those surrounding the adjacent large vessels (the abdominal aorta and its major branches including the celiac axis, the superior mesenteric artery, and the renal arteries). The specific nodal groups include: the anterior pancreaticoduodenal nodes (superior and inferior), the posterior pancreaticoduodenal nodes (supe- rior and inferior), the pyloric nodes (adjacent to the pylorus), the gastroduode- nal nodes (adjacent to the gastroduodenal artery), the hepatic nodes (adjacent to the common bile duct and the hepatic artery), the cystic node (adjacent to the choledochal cystic duct), the superior mesenteric nodes, the celiac nodes, the supra- and infrapancreatic nodes (located along the superior and inferior borders of the pancreas, respectively), the mesocolic nodes, the splenic nodes, and the gastrosplenic nodes. Some anatomic studies have shown primary lym- phatic drainage into the renal nodes as well. Although the nodes located closest to the regional subdivisions of the pancreas (head, body, and tail) are the primary lymphatic drainage stations for those zones, all of the specific nodal groups named above are included in the N category for the pancreas (Figures 18.3, 18.4). Anatomic division of the regional lymph nodes is not necessary;
however, separately submitted lymph nodes should be reported as submitted.
Metastatic Sites. Distant spread occurs commonly to the liver, peritoneal cavity, and lungs. Metastases to other sites are uncommon (or rarely detected),
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Superior to head Cystic duct node
Pyloric Hepatic nodes
Splenic nodes Superior
to body
Inferior to head
Inferior to body
Inferior to tail Superior
pancreaticoduodenal nodes (Anterior and posterior) Inferior
pancreaticoduodenal nodes (Anterior and posterior)
Inferior pancreatic nodes Superior pancreatic nodes
Hilum of spleen Superior
to tail
FIGURE 18.3. Regional lymph nodes of the pancreas (anterior view).
possibly because of the short interval from diagnosis of distant metastasis to death.
DEFINITIONS Primary Tumor (T)
TX Primary tumor cannot be assessed T0 No evidence of primary tumor Tis Carcinoma in situ
T1 Tumor limited to the pancreas 2 cm or less in greatest dimension (Figure 18.5)
T2 Tumor limited to the pancreas more than 2 cm in greatest dimension (Figure 18.5)
T3 Tumor extends beyond the pancreas but without involvement of the celiac axis or the superior mesenteric artery (Figures 18.6A–C)
T4 Tumor involves the celiac axis or the superior mesenteric artery (unre- sectable primary tumor) (Figure 18.7)
Regional Lymph Nodes (N)
NX Regional lymph nodes cannot be assessed N0 No regional lymph node metastasis
N1 Regional lymph node metastasis (Figures 18.8A–D) Distant Metastasis (M)
MX Distant metastasis cannot be assessed M0 No distant metastasis
M1 Distant metastasis
Superior mesenteric nodes Hepatic
nodes
Celiac nodes
Splenic nodes
Superior pancreatic nodes
FIGURE 18.4. Regional lymph nodes of the pancreas (anterior view with pancreatic body removed to reveal retroperitoneal vessels and lymph nodes).
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T1 T2
>2 cm
£2 cm Portal vein
Aorta
Superior mesenteric artery Celiac axis
Common bile duct
Superior mesenteric vein
FIGURE 18.5. T1 (left of dotted line) is defined as tumor limited to the pancreas 2 cm or less in greatest dimension. T2 (right of dotted line) is defined as tumor limited to the pancreas more than 2 cm in greatest dimension.
T3 T3
Peripancreatic
Portal vein Celiac axis
Common bile duct
Superior mesenteric vein
Superior mesenteric artery
A
FIGURE 18.6. A. Two views of T3, which is defined as tumor that extends beyond the pancreas but without involvement of the celiac axis or the superior mesenteric artery. Left of the dotted line: tumor invades the common bile duct without involving the superior mesenteric artery. Right of the dotted line: tumor invades peripancreatic tissues without involving the celiac axis.
T3
Duodenum
Portal vein Celiac axis
Superior mesenteric vein
Superior mesenteric artery
B T3
Duodenum
Spleen Portal vein
Aorta
Superior mesenteric vein
Superior mesenteric artery Celiac axis
Common bile duct
C
FIGURE 18.6. B. T3: tumor invades duodenum without involvement of the superior mesenteric artery. C. T3: tumor invades spleen without involvement of celiac axis or superior mesenteric artery.
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T4
T4 Duodenum
Portal vein
Aorta
Superior mesenteric vein
Superior mesenteric artery Celiac axis
Common bile duct
FIGURE 18.7. Two views of T4, which is defined as tumor involving the celiac axis (above dotted line) or (below dotted line) the superior mesenteric artery (unresectable primary tumor).
N1
Portal vein
Aorta
Superior mesenteric vein
Celiac axis
Common bile duct
Body of of pancreas
Tail of of pancreas Uncinate process
Head of pancreas
Superior mesenteric artery
A
FIGURE 18.8. A. N1 is defined as regional lymph node metastasis. Here, the primary tumor and single nodal metastasis are located within the head of pancreas.
N1
Portal vein
Aorta
Superior mesenteric vein
Celiac axis
Common bile duct
Body of of pancreas
Tail of of pancreas Uncinate process
Head of pancreas
Superior mesenteric artery
B
N1
Portal vein
Aorta
Superior mesenteric vein Common
bile duct
Body of of pancreas
Tail of of pancreas Uncinate process
Head of pancreas
C
FIGURE 18.8. N1 is defined as regional lymph node metastasis. B. Here, the primary tumor and multiple nodal metastases are located in the head of pancreas.
C. Here, the primary tumor is located in the body of pancreas with multiple nodal metastases in the head and body of pancreas.
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
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N1
Portal vein
Aorta
Superior mesenteric vein Common
bile duct
Body of of pancreas
Tail of of pancreas Uncinate process
Head of pancreas
D
FIGURE 18.8. D. N1 is defined as regional lymph node metastasis. Here, the primary tumor is located in the tail of pancreas with multiple nodal metastases in the tail of pancreas and hilum of spleen.
