Syndrome of bilateral pheochromocytoma, medullary thyroid carcinoma and multiple neuromas. A possible regulatory defect in the differentiation of chromaffin tissue.

Abstract Although the association of pheochromocytoma and thyroid tumors has been recognized for some time, only in recent years has the amyloid-producing medullary thyroid carcinoma been specifically implicated. Mucosal neuromas and parathyroid adenomas subsequently have been added to the clinical spectrum of this syndrome. Three cases illustrating the variable manifestations of this disorder are presented. It is likely that the medullary carcinoma cell is of ultimobranchial origin and that it may elaborate calcitonin, with subsequent reactive parathyroid hyperplasia. The medullary cell may be derived from neural-crest tissue, and the entire syndrome may therefore be explained on the basis of a heritable defect in a single cellular system.