From nodule to differentiated thyroid carcinoma: contributions of molecular analysis in 2012.

Today there is a better understanding of the events involved in the initiation and progression of thyroid cancer. It is indeed now known that BRAF and RAS mutations and RET/PTC and PAX8/PPARγ rearrangements account for the majority of molecular alterations detected in differentiated thyroid cancers. Abnormal regulation of microRNAs (miRNAs) is also a promising way of research. The diagnostic utility and prognostic value of detecting these molecular events has been analyzed in several recent studies. BRAF mutation analysis improves the performance of fine-needle aspiration diagnosis by increasing specificity in "indeterminate" cytologies and sensitivity in false negatives. Testing for a "panel of mutations" (BRAF, RAS, RET/PTC and PAX8/PPARγ) improves the performance, detecting papillary carcinomas with non-classic histology. The specificity of these analyzes is excellent but their sensitivity is still insufficient. In the future, specific miRNAs expression profiles in thyroid carcinoma and identification of new mutations might provide interesting information. Several studies have found that BRAF mutations are associated with a more aggressive tumor behavior, a higher risk of recurrence and treatment failure. With regard to the other mutations and rearrangements, current data are conflicting and it seems premature to draw practical conclusions applicable in routine practice. Lastly, targeted therapy with tyrosine kinase inhibitors, based on our understanding of the molecular mechanisms of thyroid oncogenesis, has shown promise in metastatic, progressive, and radioactive iodine-refractory differentiated thyroid carcinomas.