Role of Molecular Tests in the Cytologic Distinction of Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features, Classic Variant Papillary Thyroid Carcinoma and Follicular Variant Papillary Thyroid Carcinoma

In the World Health Organization classification of endocrine organs in 2017; Noninvasive follicular variant papillary thyroid carcinoma (FVPTC) was named as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). It is aimed to avoid overtreatments such as total thyroidectomy and radioactive iodine therapy. 2015 American Thyroid Association (ATA) guide recommends applying molecular tests to uncertain categories in the Bethesda reporting system. In our study, BRAF, KRAS and NRAS tests were applied to the cytology materials of NIFTP/FVPTC/classical variant papillary thyroid carcinoma (CVPTC), and the contribution of these tests to the preoperative differential diagnosis was investigated. In current study 31 FVPTK, 64 NIFTP and 12 CVPTC, operated on between 2010 and 2020 and have sufficient cytology material, were evaluated. BRAF, KRAS, NRAS mutations were examined by Real-Time PCR method in cytology materials. NRAS mutation was observed 30% of NIFTPs, %15 of FVPTC, %13 of CVPTC. KRAS mutation was observed 7% of NIFTPs, %3 of FVPTC, %9 of CVPTC. BRAFV600E mutation was observed %15 of FVPTC, %63 of CVPTC but none of NIFTP showed BRAF mutation. There is a statistically significant difference between tumor types and BRAF mutation. However there were no statistically significant difference between KRAS and NRAS mutation status and tumor types. BRAF mutation testing of thyroid fine needle aspirations could improve preoperative diagnosis of nodules, thereby reducing unnecessary surgery.