Prognostic Significance of Somatic RET Oncogene Mutations in Sporadic Medullary Thyroid Cancer: A 10-Year Follow-Up Study

Background: Medullary thyroid carcinoma (MTC) is a well-differentiated thyroid tumor that maintains the typical features of C cells. An advanced stage and the presence of lymph node metastases at diagnosis have been demonstrated to be the most important bad prognostic factors. Somatic RET mutations have been found in 40–50% of MTCs. Although a relationship between somatic mutations and bad prognosis has been described, data are controversial and have been performed in small series with short-term follow ups. The aim of this study was to verify the prognostic value of somatic RET mutations in a large series of MTCs with a long follow up. Methods: We studied 100 sporadic MTC patients with a 10.2 yr mean follow-up. RET gene exons 10–11 and 13–16 were analyzed. The correlation between the presence/absence of a somatic RET mutation, clinical/pathological features, and outcome of MTC patients was evaluated. Results: A somatic RET mutation was found in 43 of 100 (43%) sporadic MTCs. The most frequent mutation (3...