Thyroid cancer accounts for 1.5% of all
malignancies in the U.S., and it is the most common endocrine
malignancy. Detection of
thyroid cancer mostly relies on evaluation of
thyroid nodules, which are very common but only 5%-7% harbor
malignancy. Fine-needle aspiration biopsy (FNAB) is currently the most important tool for the evaluation of
thyroid nodules; however, it is limited in that it provides only a cytology assessment of the aspirated cells, and indeterminate diagnoses are present in up to 30% of FNAB results. This limitation can be overcome by the molecular analysis of FNAB, and more specifically with the use of
microRNAs (miRs). miRs constitute a class of endogenous
small noncoding RNA fragments that regulate gene expression, and in vitro studies have shown that miRs play a significant role in
cancer and regulate major processes, such as proliferation, differentiation, and cell death. Several studies have investigated the miR expression signature in different
thyroid cancers, and data support its use as a diagnostic tool that is highly accurate for
thyroid nodules. The purpose of this study is to review the accumulated data on miR dysregulation in the different
thyroid cancer types, critically assess its diagnostic utility, and conclude with future study strategies.