The value of miRNA in diagnosing thyroid cancer: a systematic review

Thyroid cancer is the most common endocrine neoplasm accounting for approximately 1,7% of total cancer diagnoses. The gold standard for evaluation of thyroid nodules is cytology from fine needle aspiration. In 30% of biopsies there is no conclusive diagnosis and patients undergo a diagnostic hemithyroidectomy. Somatic mutations occur frequently in thyroid cancer, the value of testing FNA biopsies on different mutation is analyzed, it improves accuracy, but their sensitivity is low. Another class of molecules with potential diagnostic value are miRNAs (miRNA, miR). MiRNAs function as gene regulators thereby controlling many cellular processes including cell growth, differentiation, proliferation, and apoptosis. Several studies have analyzed the expression of miRNAs in thyroid cancer, either by performing microarray analyses or validating a set of miRNAs. Recent reports focused on the diagnostic value of miRNAs in indeterminate FNA biopsies. In this systematic review we will provide an overview of all miRNAs found to be up- or downregulated in the different types of thyroid carcinomas, give an overview of the value of validated sets of microRNAs or single microRNAs in distinguishing malignant from benign lesions and conclude with a clinical view on future study strategies.