Molecular genetics and phenomics of RET mutations: Impact on prognosis of MTC

Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominant hereditary cancer syndrome caused by missense gain-of-function mutations of the RET proto-oncogene. Three distinct clinical subtypes of MEN 2 have been characterized: MEN 2A, MEN 2B, and familial medullary thyroid carcinoma (FMTC). The specific RET mutation may suggest a predilection toward a particular phenotype and clinical course, with strong genotype–phenotype correlations. Recommendations on the timing of prophylactic thyroidectomy and extent of surgery are based on classification of RET mutations into risk levels according to genotype–phenotype correlations. The excellent prognosis for MTC diagnosed at its earliest stage underscores the importance of prospective screening (calcitonin screening) for sporadic MTC and early diagnosis by RET-mutation analysis for hereditary MTC. MEN 2 provides a unique model for early prevention and cure of cancer and for the roles of stratified mutation-based diagnosis and therapy of carriers.