MALIGNANT ISLET-CELL TUMOR-ASSOCIATED WITH HYPERCALCEMIA

Background. Three cases of islet cell tumors of the pancreas with hype rcalcemia were studied and 16 similar cases have been Sound in a 25-ye ar review of the English-language literature. The purpose of the study was to review the cause, of the hypercalcemia and the clinical charac teristics of the tumors. Methods. Tumor tissue retrieved from paraffin -embedded blocks was studied immunohistochemically Sor both parathyroi d hormone (PTH) and PTH-related protein (PTHrP). PTH was measured in t he serum in each patient and the serum PTHrP was measured by immunoass ay in one patient. Results. One of our patients had a fatal serum calc ium level of 26.4 mg/dl. PTHrP stains were positive in two of our tumo rs, and one patient had an elevated PTHrP serum level. Serum PTH level s were normal or low in each patient. All three tumors were malignant and extremely vascular. The total group of 19 patients have in common hypercalcemia associated with a normal or low serum PTH level. Althoug h the cause of hypercalcemia has nos been proved, the tuners apparentl y produce PTHrP, because seven of eight tumors stained positive Sor PT HrP and each of the Sour patients tested had an elevated PTHrP serum t iter. The tumors are extremely vascular are usually malignant (17 of 1 8), and become large, but they are compatible with a relatively long p atient survival time. Conclusions. These neuroendocrine tumors associa ted with hypercalcemia share several characteristics, but a claim that they represent another type of ''functioning islet cell tumor'' shoul d await a clearer delineation of the cause of the hypercalcemia.