Sporadic pancreatic polypeptide secreting tumors (PPomas) of the pancreas

Sporadic pancreatic neuroendocrine tumors, which predominantly secrete pancreatic polypeptide (PPoma), are rare and have not been associated with a clinical syndrome. A wider understanding of their pathological features and behavior is needed.

Four PPoma patients who presented with nonspecific abdominal pain are described. Their diagnosis was established by the presence of an enhancing solitary pancreatic tumor on computed tomography (CT) and elevated fasting pancreatic polypeptide hormone levels. Patient 1 was treated with a pancreatoduodenectomy because of elevation of serum CEA level. Two of the cases underwent enucleation because of prolonged stable CT appearance. Patient 4 underwent distal pancreatectomy for a pancreatic neck tumor causing ductal obstruction and distal parenchymal atrophy.

All cases had benign histological features apart from patient 1 whose tumor demonstrated occasional mitotic activity. These tumors have not recurred after a median of 49 (range, 35-57) months. The protein expression in the tumor tissue was measured by SELDI-TOF MS and was different than the profile of pancreatic adenocarcinoma that was previously demonstrated in our laboratory. This may lead to future helpful diagnostic testing on fine needle aspirates.

Resection of sporadic PPomas presenting as a solitary well-defined mass with benign histological features results in good long-term survival.