Micro-RNAs in thyroid neoplasms: molecular, diagnostic and therapeutic implications

Micro-RNAs (miRNAs) belong to a class of small non-coding messenger RNA species that have emerged as potent regulators of a variety of biological processes including oncogenesis. They serve as master regulators with a single miRNA capable of regulating as many as 100 different target genes. Thyroid carcinomas encompass a wide spectrum ranging from well-differentiated thyroid carcinomas to poorly differentiated and anaplastic carcinoma. Currently, a considerable degree of interobserver variability exists in the morphological diagnosis of certain types of thyroid carcinomas especially the follicular pattern neoplasm. The prediction of progression of these differentiated carcinoma to more aggressive forms like poorly differentiated and anaplastic types is of considerable interest to physicians and pathologists for determining prognosis and making therapeutic decisions. Several investigators have proposed a more cohesive approach to thyroid cancer diagnosis incorporating molecular and proteomics based tools in addition to the conventional morphological diagnosis. In this context, miRNAs serve as an important diagnostic tool, and several studies have demonstrated their utility as class identifiers especially in the context of follicular thyroid carcinoma, papillary thyroid carcinoma and anaplastic thyroid carcinoma. Larger studies and/or meta-analyses could further delineate their role in predicting cancer progression and prognosis. In the same vein, miRNAs and their target genes could be targeted for novel therapeutics in the future.