Immunoreactive somatostatin in catecholamine-producing extra-adrenal paraganglioma

A patient with catecholamine-producing extra-adrenal paraganglioma was found to have a high concentration of immunoreactive somatostatin (IR-SRIF) in the peripheral blood plasma (47.0 pg/ml, normal; 13.3 +/- 5.3 pg/ml, mean +/- SD). After removal of the tumor, the plasma SRIF level fell within normal range (8.7 pg/ml). In the resected tumor, a considerable amount of IR-SRIF (71.0 ng/g wet weight)( was also detected and SRIF-positive tumor cells were demonstrated by the immunoperoxidase technique. Chromatographic analysis of an extract of the tumor showed the presence of two IR-SRIF components of large molecular size besides a component consistent with authentic tetradecapeptide SRIF (SRIF 14), and one of these had the same molecular size as octacosapeptide SRIF (SRIF 28). This seems to be the first report of a catecholamine-producing extra-adrenal paraganglioma that produces IR-SRIF with molecular heterogeneity.