Ten pheochromocytomas (five from patients with multiple endocrine neoplasia type 2 and five sporadic) were stained immunohistochemically with antibodies to calcitonin (CT) and calcitonin gene-related peptide (CGRP) by means of the peroxidase-antiperoxidase method. CGRP positive cells were found in variable numbers in all of the investigated tumors. No demonstrable difference was noted between the hereditary tumors and the sporadic tumors. Staining with CT antibody also showed cells with a positive reaction in eight of ten tumors. The distribution of the two peptides was similar, and in some cells their coexistence was visualized. Pheochromocytomas thus represent an alternative site to medullary thyroid carcinoma for CT and CGRP production. The possible influence of this on serum peptide levels needs investigation
