The mode of lymphatic and local spread of pancreatic carcinomas less than 4.0 cm in size.

To clarify the mode of lymphatic and local spread of small pancreatic carcinomas, we studied the histopathology of 33 patients with invasive ductal adenocarcinoma of the head of the pancreas less than 4 cm in diameter. Microscopically, lymph node metastases were found in 72.7% (24 of 33) of the patients: 17 patients had lymph node metastases at the first barrier and 7 patients had lymph node metastases at the second barrier. Capsular invasion was present in 21.2% (7 of 33) patients, retroperitoneal invasion in 84.8% (28 of 33) patients. Invasion to the common hepatic artery was identified in 9.1% (3 of 33) patients, and invasion to the portal vein system in 24.2% (8 of 33) patients. In addition, five of the seven patients with lymph node metastases at the second barrier had spread to the periaortic lymph nodes. Thus, even patients with small pancreatic cancers which were macroscopically confined to the pancreas showed microscopic extrapancreatic tumor extension, especially invasion to the retroperitoneal tissues and to the periaortic lymph nodes. This suggests that an aggressive surgical approach, including complete resection of surrounding connective tissues in the retroperitoneum and extensive lymph node dissection, is necessary to improve the surgical therapeutic results even for small pancreatic cancers.