Validation of the VE1 immunostain for the BRAF V600E 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 to 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 showed 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.

Keywords: dermatopathology; immunohistochemistry; melanoma.

Figure 1

BRAF wild type melanoma in a lymph node that is negative for VE1 immunostain alongside a 3+ positive capsular melanocytic nevus (Original magnification ×100).

Figure 2

BRAF wild type melanoma with 1+ weak cytoplasmic and nuclear blush on VE1 immunostain (Original magnification ×200).

Figure 3

A, BRAF V600E mutant primary melanoma with positive staining for VE1 (×200). B, Corresponding BRAF V600E metastatic melanoma with positive staining for VE1 in the same patient (Original magnification ×100).

Figure 3

A, BRAF V600E mutant primary melanoma with positive staining for VE1 (×200). B, Corresponding BRAF V600E metastatic melanoma with positive staining for VE1 in the same patient (Original magnification ×100).