DIAGNOSTIC PROBLEMS IN MEDULLARY CARCINOMA OF THE THYROID

Medullary carcinoma of the thyroid (MCT), the tumor entity related to parafollicular C cells of the thyroid gland, is characterized by pecul iar morphological, functional and behavioral features. Apart from the constant finding of calcitonin production by MCT, heterogeneous patter ns of growth as well as different associations with other lesions in t he setting of MEN II syndrome have been observed. This review addresse s these points, as were discussed at the 1992 European School of Patho logy courses. Heterogeneity of histological patterns of MCT suggests c aution in the interpretation of any thyroid tumor. Immuohistochemical demonstration of calcitonin is apparently the only valid criterion for a differential diagnosis. A correct identification of MCT is importan t for the individual patient (to plan proper therapy) but also for pat ient's relatives to screen other familiar cases in the setting of MEN II syndromes.