Medullary carcinoma of the thyroid.

Medullary carcinoma is an unusual malignant neoplasm. The cell of origin is considered to be the C-cell which is derived from the ultimobranchial body and neural crest. The tumor is solid and has characteristic amyloid in the stroma. The lesion usually presents as a neck mass, and multicentricity is not unusual. In some patients diarrhea may be an important presenting symptom. Serum calcitonin is typically elevated and is important in the diagnostic confirmation. About 10 percent of the cases are part of a familial endocrine syndrome which includes pheochromocytomas, mucosal neuromas, and other endocrine gland adenomas. Frequent multicentricity and early cervical lymphatic and systemic metastases necessitate total thyroidectomy and radical neck dissection. Prognosis varies from a rapid demise to long term survival.