Pheochromocytoma and medullary carcinoma of thyroid

Abstract

Three members of a kindred exhibiting pheochromocytoma and amyloid-producing medullary carcinoma of thyroid are presented to support the belief that this syndrome is a distinct clinical entity and is probably genetically determined. Ultrastructural studies of the pheochromocytoma and the medullary carcinoma were carried out in one case. In the pheochromocytoma typical secretory granules identical to those described in the normal and neoplastic adrenal medullary cells were found. In medullary carcinoma of the thyroid distinct and characteristic secretory granules were shown for the first time by electron microscopy and a close relationship between the secretory granules and the local amyloid deposits was observed. A possible mechanism for local amyloid formation in this tumor was discussed. Morphology of the secretory granules of medullary carcinoma of the thyroid was different from that of pheochromocytoma but resembled that described in the parafollicular cells of the thyroid in rats. The finding of secretory granules in medullary carcinoma may facilitate the establishment of its cell origin.