Pancreatic polypeptide islet cell tumor: case report and review of the literature.

Pure pancreatic polypeptide-containing tumors (PPomas) are quite rare. Only 20 cases have been described. In this article we report a 75-year-old woman with such an endocrine islet cell tumor. The patient had no specific symptoms that could be ascribed to the tumor. An abdominal CT scan revealed a 3 cm soft tissue mass arising inferiorly from the tail of the pancreas. Local resection by way of a distal pancreatectomy was performed. A well-circumscribed hemorrhagic multiloculated mass, 3.7 cm in greatest dimension, was present in the tail of the pancreas. The patient has remained well and tumor free for the past 22 months. The endocrine characterization of the tumor was achieved by means of immunohistochemical analysis. Staining specific for insulin, glucagon, somatostatin, and gastrin was negative. In contrast, staining of the tumor for pancreatic polypeptide was strongly positive. A number of nonfunctioning islet cell tumors of the pancreas have been described. The lack of function has previously been suggested to indicate the lack of secretion of an endocrine product. This report documents that islet cell tumors may function by secreting pancreatic polypeptide but not cause symptoms.