Abstract: Objective To investigate the significance of BRAF^V600E in the detection of benign,malignant and borderline thyroid lesions. Methods A total of 273 formalin fixed and paraffinembedded specimens of papillary thyroid carcinoma (PTC) were selected for study from January 2010 to December 2018 .There were 254 cases of classical variant of papillary carcinoma (CVPTC) and 19 cases of follicular variant of papillary carcinoma (FVPTC).30 benign lesions were made into tissue microarray (TMA),and 17 uncertain borderline lesions diagnosed by HE.Polymerase chain reaction (PCR) was used to detect 17 cases of CVPTC 12 cases of FVPTC 17 cases of borderline lesions and 13 cases of benign lesions. BRAF^V600E gene mutation and protein expression were observed. Results The positive expression rates of BRAF^V600E protein in CVPTC,FVPTC,borderline lesion and benign lesion were 86.6%,15.9%,23.5% and 26.7%,respectively.Mutation rates of BRAF^V600E gene in CVPTC,FVPTC,borderline lesions and benign lesions were 82.4%,41.7%,23.5% and 0,respectively.There were significant differences in expression of BRAF^V600E protein in CVPTC,FVPTC,borderline lesions and benign lesions(P＜0.05).There was statistically significant difference between BRAF^V600E gene mutation in CVPTC and FVPTC and borderline diseases(P＜0.05).The coincidence coefficient between BRAF^V600E gene mutation and protein expression in CVPTC was K=0.821,P＜0.05.It was statistically significant.The positive expression of BRAF^V600E protein in PTC was not correlated with gender,age,tumor size and lymph node metastasis (P＞0.05),but was correlated with tissue type and capsule invasion (P＜0.05). Conclusion BRAF^V600E has reference value in the diagnosis and differential diagnosis of benign and malignant thyroid and borderline thyroid lesions.

Key words: BRAF^V600E, papillary thyroid carcinoma, borderline lesion, immunohistochemistry