Low prevalence of the somatic M918T RET mutation in micro-medullary thyroid cancer.

Background: The prevalence of RET somatic mutations in sporadic medullary thyroid cancer (MTCs) is ∼40%–50%, and the most frequent somatic mutation is M918T. RET-positive MTCs have been demonstrated to have a more advanced stage at diagnosis and a worse outcome. Aims: The aim of the present work was to compare the prevalence of RET somatic mutations in sporadic microMTCs ( 1 and 2 and 3 cm. Results: The overall prevalence of the somatic M918T RET mutation was 19.4% (31/160). RET mutations were distributed differently among the four groups. The prevalence was 11.3% (6/53) in group A, 11.8% (8/68) in group B, 31.8% (7/22) in group C, and 58.8% (10/17) in group D, exhibiting an increase with increasing size of the tumor. When comparing the prevalence of mutations in the four groups, we found a lo...