Secondary tumors of the pancreas: an analysis of a surgical and autopsy database and review of the literature.

The vast majority of pancreatic carcinomas are primary, and, among these, more than 90% are of ductal origin. However, a variety of extrapancreatic tumors may involve the pancreas secondarily and may manifest different clinicopathological characteristics and outcomes. In this study, pathology material from 973 surgical specimens and 4955 adult autopsy cases was reviewed to identify the tumors metastatic to or secondarily involving the pancreas. Biliary and periampullary neoplasms and tumors confined to peripancreatic soft tissue were excluded. In the autopsy series, the pancreas was involved by tumor in 190 cases, and 81 of these were secondary tumors. These were predominantly of epithelial origin, most commonly from lung (34), followed by GI tract (20), kidney (4), breast (3), liver (2), ovary (1), and urinary bladder (1). In addition, there were six tumors of hematopoietic origin, two melanomas, two sarcomas, and two mesotheliomas. Among the 973 surgical specimens, 38 cases contained metastatic tumors to the pancreas. Of these, 11 were lymphomas, and the others were carcinomas of stomach (7), kidney (6), lung (2), liver, prostate, ovary, uterus (1 case of each), and a Merkel cell carcinoma. In addition, there were three malignant gastrointestinal stromal tumors and one retroperitoneal leiomyosarcoma. In conclusion, lung cancer is the most common source of metastasis to pancreas, followed by gastrointestinal carcinomas and lymphomas. These tumors are usually seen in patients with disseminated disease and are detected mainly in autopsies. Secondary tumors constitute about 4% of pancreatic specimens in the authors' surgical database. Approximately one-third of them are clinically mistaken as primary tumors of the pancreas. These are predominantly hematopoietic malignancies or carcinomas of renal or gastric origin. Secondary tumors should be entertained in both the clinical and pathological differential diagnosis of pancreatic neoplasia.