Expression of BRAF V600E mutant protein in cutaneous malignant melanoma

Objective To detect the expression of BRAF V600E mutant protein in cutaneous malignant melanoma (CMM),and to evaluate the sensitivity and specificity of immunohistochemistry (IHC) in detecting BRAF V600E mutation.Methods IHC with an anti-BRAF V600E monoclonal antibody was performed to detect the expression of BRAF V600E mutant protein in paraffin-embedded tissue sections from 103 patients with CMM and 40 patients with nevus.Statistical analysis was carried out with SPSS software version 17.0,and the expression rate of BRAF V600E mutant protein was compared by chi-square test.Results The expression rate of BRAF V600E mutant protein in the CMM patients was 20.4％ (21/103),significantly higher than that in the nevus patients (5.0％ (2/40),x2 =5.06,P ＜ 0.05).Significant differences were observed in the expression rate of BRAF V600E mutant protein between CMM patients of different age groups (29.8％ (14/47) in patients aged ＜ 60 years vs.12.5％ (7/56) in those aged ≥ 60 years,P ＜ 0.05) and nationality (30.2％ (13/43) for Uygur nationality vs.13.3％ (8/60) for Han nationality,P ＜ 0.05),as well as among CMM lesions from different anatomical sites (13.6％ (6/42) in acral sites vs.11.8％ (4/29) in mucous membrane vs.45.8％ (11/32) in non-acral sites,P ＜ 0.05) and of different Clark levels (8.6％ (4/42) for grade Ⅰ-Ⅲ vs.12.4％ (17/61) for grade Ⅳ-Ⅴ,P＜ 0.05),but not between male and female CMM patients or between CMM patients with lymph node metastasis and those without (both P ＞ 0.05).IHC with the anti-BRAF V600E antibody showed a sensitivity of 100％ (15/15) and a specificity of 98.5％ (65/66) in detecting BRAF V600E mutation.Conclusions The expression of BRAF V600E mutant protein is up-regulated in CMM lesions,and CMM patients of Uygur nationality seems to have a higher expression rate than those of Han nationality.IHC appears to be an accurate and rapid method to detect V600E BRAF mutation.\r\n\r\nKey words: \r\nMelanoma;  Mutation;  Proto-oncogene proteins B-raf