[Calcitonin cancers: definition, history, various forms].

Calcitonin secreting tumors, as their name indicates, share a common denominator; yet, their clinical, morphological and biochemical features are polymorphous. Medullary thyroid carcinoma is a well-known disease, with sporadic and familial forms, associated or not with type II multiendocrinopathy; not only calcitonin and carcinoembryonic antigen, its reliable markers, but also multiple other hormones may be secreted. Atypical forms, more or less undifferentiated, even heterogenous may also exist: the presence of the hormone in tumoral cells allows their recognition. Moreover, ectopic calcitonin secretion may be related to quite different tumors with regard to their clinic, pathologic, embryologic aspects. Thus, strict criteria are necessary for their diagnosis. Molecular biology will certainly help the understanding of the functional and genetic aspects of these tumors.