Classification and staging of pancreatic nonendocrine tumors.

Pancreatic nonendocrine tumors are classified according to their histogenetic origin. This results in tumor entities that differ in biology and prognosis. Ductal adenocarcinoma is the dominating pancreatic tumor. Although its morphology is well known, our knowledge of its biology is limited. A grading system is presented for a better individual characterization of ductal adenocarcinoma. The tumor's poor prognosis is due to an early spread to retroperitoneal tissues. This most likely accounts for tumor recurrence so frequently seen after "curative" resection. Tumors other than ductal adenocarcinoma comprise only a minority of pancreatic neoplasms but must not be neglected because of their particular biological features.