Relationship of metastatic medullary thyroid carcinoma to calcitonin content of pheochromocytomas: an immunohistochemical study.

Immunoperoxidase studies have been utilized to investigate further the previously reported presence of immunoassayable calcitonin in pheochromocytoma tissue from some patients with MEN II syndromes. We have been able to demonstrate calcitonin in pheochromocytoma tissue only in two patients with MEN II syndromes in whom the pheochromocytomas contained metastatic medullary thyroid carcinoma. In both cases, the calcitonin was present only in the medullary carcinoma. We have not been able to demonstrate immunoreactive calcitonin in normal adrenal glands or in pheochromocytomas of other patients with and without MEN syndromes. Adrenal medullary cells and thyroid C cells are both of neural crest origin and both possess APUD characteristics. The presence of calcitonin in medullary thyroid carcinoma cells and not in pheochromocytes has important implications with regard to cellular differentiation and peptide hormone production.