J Pathol Transl Med.  2018 May;52(3):157-163. 10.4132/jptm.2018.03.28.

Utility of BRAF VE1 Immunohistochemistry as a Screening Tool for Colorectal Cancer Harboring BRAF V600E Mutation

• Kwon JH
• Jeong BK
• Yoon YS
• Yu CS
• Kim J

• KMID: 2412927
• DOI: http://doi.org/10.4132/jptm.2018.03.28

Abstract

BACKGROUND
BRAF mutation has been recognized as an important biomarker of colorectal cancer (CRC) for targeted therapy and prognosis prediction. However, sequencing for every CRC case is not cost-effective. An antibody specific for BRAF V600E mutant protein has been introduced, and we thus examined the utility of BRAF VE1 immunohistochemistry for evaluating BRAF mutations in CRC.
METHODS
Fifty-one BRAF-mutated CRCs and 100 age and sexmatched BRAF wild-type CRCs between 2005 and 2015 were selected from the archives of Asan Medical Center. Tissue microarrays were constructed and stained with BRAF VE1 antibody.
RESULTS
Forty-nine of the 51 BRAF-mutant CRCs (96.1%) showed more than moderate cytoplasmic staining, except for two weakly stained cases. Six of 100 BRAF wild-type cases also stained positive with BRAF VE1 antibody; four stained weakly and two stained moderately. Normal colonic crypts showed nonspecific weak staining, and a few CRC cases exhibited moderate nuclear reactivity (3 BRAF-mutant and 10 BRAF wild-type cases). BRAF-mutated CRC patients had higher pathologic stages and worse survival than BRAF wild-type patients.
CONCLUSIONS
BRAF VE1 immunohistochemistry showed high sensitivity and specificity, but occasional nonspecific staining in tumor cell nuclei and normal colonic crypts may limit their routine clinical use. Thus, BRAF VE1 immunohistochemistry may be a useful screening tool for BRAF V600E mutation in CRCs, provided that additional sequencing studies can be done to confirm the mutation in BRAF VE1 antibody-positive cases.

Keyword

Colorectal neoplasms; BRAF mutation; Immunohistochemistry; DNA sequencing

MeSH Terms

Cell Nucleus
Chungcheongnam-do
Colon
Colorectal Neoplasms*
Cytoplasm
Humans
Immunohistochemistry*
Mass Screening*
Mutant Proteins
Prognosis
Sensitivity and Specificity
Sequence Analysis, DNA
Mutant Proteins

Figure

• 

  Fig. 1. Various staining patterns for BRAF VE1 immunohistochemistry (IHC). (A–C) BRAF VE1 is stained in cytoplasm with variable intensities in BRAF-mutated colorectal cancers (CRCs). 1+, faint (A); 2+, moderate (B); and 3+, strong (C). (D–F) Representative figures for cases with discrepancies between BRAF VE1 IHC and BRAF sequencing results. Negative staining in a BRAF-mutated CRC (D); 1+, faint cytoplasmic staining in a BRAF wild-type CRC (E); and 2+, moderate cytoplasmic staining in a BRAF wild-type CRC (F). (G–I) Representative figures for cases showing nuclear BRAF VE1 staining. (G) A BRAF-mutated CRC showing nuclear staining as well as moderate cytoplasmic staining. (H) A BRAF wild-type CRC showing only nuclear staining. (I) Non-neoplastic colonic crypts showing strong nuclear and faint cytoplasmic staining. Mut., BRAF-mutated CRCs; WT, BRAF wild-type CRCs.

• 

  Fig. 2. BRAF-mutated colorectal cancer (CRC) patients have shorter overall (A) and progression-free survival (B) periods (p<.001).

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  Fig. 3. BRAF-mutated colorectal cancer patients with high immunohistochemistry (IHC) intensity generally showed shorter overall (A) and progression-free survival (B) than patients with low IHC intensity (p>.05).

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