Familial nonmedullary thyroid carcinoma.

It is well-known that medullary thyroid carcinoma occurs in a familial form as part of the multiple endocrine neoplasia (MEN) 2 syndromes. However, it is less well-recognized that nonmedullary thyroid carcinoma (NMTC) sometimes is familial. Arising from the thyroid epithelial cell, the NMTCs include papillary, follicular, and anaplastic thyroid carcinoma. Although most NMTC are sporadic, there is increasing evidence for a familial form. When inherited, NMTC is autosomal dominant with partial penetrance, and it is not associated consistently with other malignancies. The average age of onset is about 38 years, and in some cases, it may be more aggressive than sporadic PTC; up to 5% of subjects with NMTC have a family history positive for the same disorder. The etiologic gene(s) have not been identified, although positional cloning of these genes may be possible. The evidence for and characteristics of familial NMTC will be reviewed, and the clinical and research implications will be discussed.