Optimization of fine-needle aspiration biopsy of the thyroid nodes in complex diagnostic situations

Purpose of the study . To identify the most informative combinations of small non-coding RNA molecules (miRNA) associated with malignant tumors of the thyroid gland (TG) in patients with nodular formations with an uncertain conclusion based on fine needle aspiration biopsy (FNA) and the absence of gene mutations. Materials and methods . The study included 83 patients with thyroid nodules according to the results of ultrasound examination with an indefinite cytological conclusion based on FAB materials (category III–V according to the Bethesda classification) and the absence of V600E mutations in the BRAF gene, NRAS, HRAS, KRAS genes in the molecular genetic study of the aspirate. Expression activity of miRNA was determined by realtime PCR in aspirate. Using cluster analysis, homogeneous groups of miRNAs associated with malignant thyroid lesions in patients were identified. Results . In the cells of thyroid nodules obtained during FNA, malignant lesions are associated with an increase in the expression activity of miRNA‑146b,–221,–222,–885–5p and a decrease in the expression of miRNA‑455–3p and miRNA‑574–3p. Reciprocal changes in expression activity in pairs miRNA‑146b/miRNA‑574–3p, miRNA‑221/miRNA‑455–3p, miRNA‑222/miRNA‑574–3p, miRNA‑885–5p/miRNA‑574–3p are more informative when differential diagnosis of benign and malignant thyroid formations than assessing the expression of individual miRNAs. Conclusion. With an uncertain cytological conclusion based on the FAB data of thyroid nodules (categories III–V according to the Bethesda classification) and negative results of a molecular genetic study regarding gene mutations, it is recommended to direct further diagnostic search in determining the expression in the aspirate of miRNA‑146b,–221,–222,–885–5p,–455–3p,–574–3p.