[Medullary cancer of the thyroid].

INTRODUCTION: Medullary thyroid carcinoma is a rare disease which originates from the secretion of calcitonin by thyroid parafollicular cells. Sporadic (75%) and inherited (25%) forms of the disease are encountered. Familial forms (termed multiple endocrine neoplasia type IIa, IIb, or familial medullary thyroid carcinoma) may or may not be associated with other endocrinopathies such as pheochromocytoma and/or hyperparathyroidism.

CURRENT KNOWLEDGE AND KEY POINTS: Circulating forms of calcitonin, a marker of the disease, are heterogeneous in blood, thus explaining why assays lead to different results according to the method used.

FUTURE PROSPECT AND PROJECTS: Family screening is much easier, as germ line mutations of the proto-oncogene RET have recently been identified in inherited forms of the disease. Treatment includes extensive surgery. This, and prophylactic thyroidectomy in gene carriers, is discussed. Prognosis is much better nowadays, but precise follow-up has to be instituted.