Thyroid cancer genetics: multiple endocrine neoplasia type 2, non-medullary familial thyroid cancer, and familial syndromes associated with thyroid cancer.

Familial thyroid cancer accounts for 25% of medullary thyroid cancer (MTC) and 5% of non-medullary thyroid cancer. All patients who have familial MTC have one of three variants of multiple endocrine neoplasia type 2 that are defined by specific mutations in the rearranged during transfection (RET) proto-oncogene. Patients who have familial nonmedullary familial thyroid cancer most likely have a mutation that is autosomal dominant with reduced penetrance. Thyroid cancer also is associated with a number of familial syndromes. This article focuses on the genetics and management of familial thyroid cancers and the syndromes associated with thyroid cancer.