In a patient with bilateral malignant familial pheochromocytomas, medullary thyroid cancer, and parathyroid adenomas (Sipple's syndrome), high concentrations of calcitonin were assayed in the medullary cancer. A striking morphological similarity is noted between the medullary thyroid carcinoma and the metastases from the pheochromocytoma in this patient. The recently reported discovery of a calcitonin-like substance in the adrenal medulla and the morphological similarities between the pheochromocytomas' metastases and the calcitonin producing thyroid cancer are considered as evidence in support of the concept that this syndrome is a defect in a single (neuroectodermal) cell system.
Paloyan E, Scanu A, Straus FH, Pickleman JR, Paloyan D. Familial Pheochromocytoma, Medullary Thyroid Carcinoma, and Parathyroid Adenomas. JAMA. 1970;214(8):1443-1447. doi:10.1001/jama.1970.03180080025005