A Nationwide Study of Multiple Endocrine Neoplasia Type 2A in Norway: Predictive and Prognostic Factors for the Clinical Course of Medullary Thyroid Carcinoma.

Background: Multiple endocrine neoplasia type 2A (MEN 2A) is an autosomal dominant syndrome caused by activating germline mutations in the RET (REarranged during Transfection) proto-oncogene. MEN 2A has a strong (>95%) and age-dependent (5-25 years) clinical penetrance of medullary thyroid carcinoma (MTC). Several major studies have analyzed the predictive and prognostic factors for MEN 2A to find indicators that predict the optimal timing of prophylactic thyroidectomy.