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.