Pancreatic polypeptide-producing tumors. Silent lesions of the pancreas?

Eight patients with pancreatic polypeptide (PP)-producing islet cell tumors and one patient with pseudo-PP-producing tumors were examined. Their age range was 20 to 74 years. Clinical features included abdominal pain in four patients, weight loss in four patients, diarrhea in two patients, gastrointestinal bleeding in two patients, and jaundice in one patient. The range of the basal serum level of PP was 394 to 35,100 pg/mL. In two patients the PP-producing tumors were associated with multiple endocrine neoplasia. Two patients had diffuse hepatic metastases at the time of diagnosis and four patients had disease limited to the pancreas. Pancreaticoduodenectomy and 80% pancreatectomy were performed in four and two patients, respectively. Immunohistochemical staining was positive for PP and neuron-specific enolase in all cases and was negative for other peptides except in one specimen with microadenomatosis. Patients who underwent curative resection are asymptomatic with normal serum levels of PP.