Validation of the VE1 immunostain for the BRAFV600E mutation in melanoma

Abstract

BACKGROUND BRAF mutation status, and therefore eligibility for BRAF inhibitors, is currently determined by sequencing methods. We assessed the validity of VE1, a monoclonal antibody against the BRAF V600E mutant protein, in the detection of mutant BRAF V600E melanomas as classified by DNA pyrosequencing. METHODS The cases were 76 metastatic melanoma patients with only one known primary melanoma who had had BRAF codon 600 pyrosequencing of either their primary (n=19), metastatic (n=57) melanoma, or both (n=17). All melanomas (n=93) were immunostained with the BRAF VE1 antibody using a red detection system. The staining intensity of these specimens was scored from 0 – 3+ by a dermatopathologist. Scores of 0 and 1+ were considered as negative staining while scores of 2+ and 3+ were considered positive. RESULTS The VE1 antibody demonstrated a sensitivity of 85% and a specificity of 100% as compared to DNA pyrosequencing results. There was 100% concordance between VE1 immunostaining of primary and metastatic melanomas from the same patient. V600K, V600Q, and V600R BRAF melanomas did not positively stain with VE1. CONCLUSIONS This hospital-based study finds high sensitivity and specificity for the BRAF VE1 immunostain in comparison to pyrosequencing in detection of BRAF V600E in melanomas.

Utility of BRAF V600E Immunohistochemistry Expression Pattern as a Surrogate of BRAF Mutation Status in 154 Patients with Advanced Melanoma

“…Heterogeneous BRAF V600E IHC expression has been reported in 2.6% to 35% of melanoma tumor samples tested [9, 10, 14, 22, 23]. Here, we also confirm heterogeneous BRAF V600E IHC expression pattern in a subset of melanomas.…”

Immunohistochemistry is highly sensitive and specific for the detection of NRASQ61R mutation in melanoma

“…22 In the current study, intratumoral heterogeneity was seen only in one case, whereas intertumoral heterogeneity in the same patient (comparison of immunohistochemistry for NRAS mutational status of primary vs paired metastatic samples) was not an aim of the current study and future investigations will assess concordance of NRAS protein expression in multiple patient's tumors. Previous immunohistochemical analyses using BRAFV600E antibody have shown that intratumoral heterogeneity of BRAF mutation is not generally observed [23][24][25] and up to 100% concordance between matched primary and metastatic melanomas has been reported. 24 These results support the routine use of immunohistochemistry with the anti-BRAFV600E antibody as an ancillary screening tool to assess the BRAFV600E mutation status in melanoma patients 26 for treatment planning.…”

“…Previous immunohistochemical analyses using BRAFV600E antibody have shown that intratumoral heterogeneity of BRAF mutation is not generally observed [23][24][25] and up to 100% concordance between matched primary and metastatic melanomas has been reported. 24 These results support the routine use of immunohistochemistry with the anti-BRAFV600E antibody as an ancillary screening tool to assess the BRAFV600E mutation status in melanoma patients 26 for treatment planning.…”

ERK/MAPK Signaling Drives Overexpression of the Rac-GEF, PREX1, in BRAF- and NRAS-Mutant Melanoma

“…Immunohistochemical staining was performed in the UNC Department of Dermatology Dermatopathology Laboratory as we have recently described (23). Briefly, freshly cut 4-μm thick sections of formalin-fixed and paraffin-embedded melanoma tissue blocks were stained using the fully automated Leica Bond III system.…”