MicroRNA expression profile of thyroid nodules in fine-needle aspiration cytology: a confirmatory series

Introduction: MiRNAs are small endogenous non-coding RNAs implicated with gene expression regulation. Changes in miRNA levels have been reported in thyroid cancer. Fine-needle aspiration cytology (FNAC) is the most reliable tool for differential diagnosis of thyroid nodules. Methods: We have analyzed 174 FNAC from 168 patients with thyroid nodules for expression levels of 11 miRNAs (miRNA197; -187; -181b-3p; -181b-5p; -224; -181a; 146b; -221; -222; -155 and miRNA183) known to be up-regulated in cancer tissues compared to benign lesions. Expression of miRNAs was analyzed in FNA samples calculating the fold change of miRNA expression relative to normal thyroid tissue after normalization to an endogenous control. Results: In FNAC, miRNA expression was confirmed to be higher in malignant or suspicious for malignancy nodules compared to benign, only for miRNA146b, -222 and -221 (fold change expression ≥ 5). Conclusion: In this study, we confirmed that a limited set of miRNAs can be used for the differential diagnosis of thyroid nodules.