Background: Approximately 10% of thyroid nodules undergoing fine needle aspiration biopsy (FNAB) receive a suspicious for follicular neoplasm (SFN) classification. Currently, there is no diagnostic tool to preoperatively discriminate between follicular adenoma (FA) and thyroid cancer (TC), and most patients require surgery to exclude malignancy.
Objectives: To characterize the micro-ribonucleic acid (miRNA) signature of tumors assessed as SFN and define circulating miRNA patterns to distinguish FA from follicular cancer in patients with thyroid nodules biopsied using FNAB.
Material and methods: The study included excised tumor and thyroid tissue samples from 80 consecutive patients collected by a pathologist in the operating theater. The miRNA was isolated from specimens at the Center for Medical Genomics OMICRON, and next-generation sequencing (NGS) was used to obtain target miRNAs. In addition, miRNA expression was detected in serum using polymerase chain reaction (PCR).
Results: Well-differentiated thyroid cancer (WDTC) samples had significantly higher expression levels of hsa-miR-146b-5p (p = 0.030) and hsa-miR-146b-3p (p = 0.032), while the expression levels of hsa-miR-195-3p were significantly lower (p = 0.032) in WDTC samples compared to FA specimens. The serum of TC patients showed markedly higher expression of the unique miRNA hsa-miR-195-3p (p = 0.039).
Conclusions: The overexpression of hsa-miR-146b-5p and hsa-miR-146b-3p, and the downregulation of hsa-miR-195-3p expression could be used as biomarkers to distinguish FA from WDTC in patients with FNAB results classified as Bethesda tier IV. In addition, hsa-miR-195-3p could act as a serum biomarker for differentiating patients with FA from those with WDTC, and preoperative measurement of its expression would help avoid unnecessary surgeries. However, this concept needs further verification in a more substantial prospective study.
Keywords: follicular adenoma; next-generation sequencing; suspicious for follicular neoplasm; thyroid cancer.