RESUMEN
BACKGROUND: The accurate diagnosis of benign and malign thyroid tumors is very important for the clinical management of patients. The distinction of thyroid papillary carcinoma follicular variant and follicular adenoma can be difficult. AIM: To investigate the alternative methods like immunohistochemistry and exon 15 in the BRAF gene 1799 T/A mutation analyses for distinguishing thyroid tumors. MATERIALS AND METHODS: We applied immunohistochemical markers; CK19, HMWCK, Galectin‑3, HBME‑1 and Fibronectin and mutant allelespecific PCR amplification technique was used to determine 1799 T/A mutation within the BRAF gene. Formalin‑fixed parafin embedded tissues from 45 surgically total resected thyroids, included 26 thyroid papillary carcinoma follicular variant (FV‑TPC), 8 Follicular Adenoma (FA), 6 Minimal invasive follicular carcinoma (MIFC) and 5 Follicular Carcinoma (FC). STATISTICAL ANALYSES USED: Pearson Chi‑Square and Kruskal Wallis tests were performed. RESULTS: There was a positive correlation between FV‑TPC and HMWCK, CK 19, HBME1, Galectin 3, fibronectin (P < 0.05), but there was no correlation with FV‑TPC and BRAF gene mutation (P > 0.05). HBME‑1 and CK 19 stained strong and diffuse positive in FV‑TPCs but weak and focal in FAs. CONCLUSION: Our study suggests that morphologic features combined with immunohistochemical panel of HMWCK, CK19, HBME‑1, Galectin‑3 and fibronectin can help to distinguish benign and malign thyroid neoplasms and FV‑TPC from follicular adenomas. BRAF gene 1799 T/A mutation has been non‑specific but its detection can be a useful tool combined with immunohistochemistry for diagnosing FV‑TPC.