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Int J Cancer. 2013 Oct 1;133(7):1624-30. doi: 10.1002/ijc.28183. Epub 2013 Apr 25.

BRAF V600E-specific immunohistochemistry for the exclusion of Lynch syndrome in MSI-H colorectal cancer.

Author information

1
Department of Neuropathology, Institute of Pathology, University Hospital Heidelberg and Clinical Cooperation Unit Neuropathology, German Cancer Research Center (DKFZ), Heidelberg, Germany.

Abstract

The differentiation between hereditary and sporadic microsatellite-unstable (MSI-H) colorectal cancer is a crucial step in Lynch syndrome diagnostics. Within MSI-H colorectal cancers, the BRAF V600E mutation is strongly associated with sporadic origin. Here, we asked whether BRAF V600E-specific immunohistochemistry (clone VE1) is helpful in separating sporadic from Lynch syndrome-associated MSI-H colorectal cancers. To that end, we performed VE1 immunohistochemistry and BRAF sequencing in a series of 91 MSI-H colorectal cancer specimens from patients tested for Lynch syndrome. Concordance of VE1 immunohistochemistry and molecular BRAF mutation status was observed in 90 of 91 (98.9%) MSI-H samples. All 11 tumors classified as BRAF V600E mutation-positive by Sanger sequencing were immunopositive, and 79 (98.8%) of 80 tumors classified as BRAF wild type showed negative staining. All VE1-positive tumors were MLH1- and PMS2-negative by immunohistochemistry. None of the tumors from mismatch repair (MMR) gene germline mutation carriers (n = 28) displayed positive VE1 staining, indicating that BRAF V600E mutation-specific immunostaining has a low risk of excluding Lynch syndrome patients from germline mutation analysis. In conclusion, implementation of VE1 immunohistochemistry was able to detect BRAF-mutated MSI-H colorectal cancers with a sensitivity of 100% and a specificity of 98.8%. Among MLH1-negative colorectal cancers, the rate of VE1-positive lesions was 21%, offering the exclusion of these patients from MMR germline testing. Therefore, we suggest the integration of VE1 immunohistochemistry into the diagnostic panel of Lynch syndrome.

KEYWORDS:

BRAF V600E; Lynch syndrome; colorectal cancer; hereditary nonpolyposis colorectal cancer; microsatellite instability

PMID:
23553055
DOI:
10.1002/ijc.28183
[Indexed for MEDLINE]
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