Calcitonin-producing pancreatic somatostatinoma

A pancreatic somatostatinoma metastatized to the liver was detected in a 70-yr-old woman presenting with chronic diarrhea, steatorrhea, pancreatic insufficiency, diabetes mellitus, and achlorhydria. At immunocytochemistry, most tumor cells stored both somatostatin and calcitoninlike substances. Chromatography of acid extracts of the tumor on G50 Sephadex gave two distinct peaks coeluting with cyclic ovine somatostatin and human calcitonin, respectively, thus ruling out the hypothesis of a single cross-reacting molecule synthetized by the neoplastic cells. When the tumor was extracted at neutral pH, larger molecular forms of the above components were found, which accounted for less than 20% of the total immunoreactivity. Gel permeation of plasma showed that the circulating calcitonin- and somatostatinlike components consisted of three and four different forms, respectively, including components of molecular weights similar to those of the reference peptides. Inhibition curves and immunoadsorption experiments indicated that the large forms were immunologically similar, if not identical, to the corresponding standard preparations. The present case illustrates the occasional ability of neoplastic somatostatin cells of pancreas to synthetize simultaneously components immunologically related to somatostatin and calcitonin. These two inappropriate secretions could account for the symptoms displayed by this patient.