title: Utility of BRAF V600E Immunohistochemistry Expression Pattern as a Surrogate of BRAF Mutation Status in 154 Patients with Advanced Melanoma.
abstract: Successful BRAF inhibitor therapy depends on the accurate assessment of the mutation status of the BRAF V600 residue in tissue samples. In melanoma, immunohistochemical (IHC) analysis with monoclonal anti-BRAF V600E has emerged as a sensitive and specific surrogate of BRAF V600E mutation, particularly when BRAF V600E protein expression is homogeneous and strong. A subset of melanomas exhibit heterogeneous labeling for BRAF V600E, but our understanding of the significance of heterogeneous BRAF V600E IHC expression is limited. We used next-generation sequencing to compare BRAF V600E IHC staining patterns in 154 melanomas: 79 BRAF(WT) and 75 BRAF (including 53 V600E) mutants. Agreement among dermatopathologists on tumor morphology, IHC expression, and intensity was excellent (ρ = 0.99). A predominantly epithelioid cell phenotype significantly correlated with the BRAF V600E mutation (P = .0085). Tumors demonstrating either heterogeneous or homogeneous IHC expression were significantly associated with the BRAF V600E mutation (P < .0001), as was increased intensity of staining (P < .0001). The positive predictive value was 98% for homogenous IHC expression compared with 70% for heterogeneous labeling. Inclusion of both heterogeneous and homogeneous BRAF V600E IHC expression as a positive test significantly improved IHC test sensitivity from 85% to 98%. However, this reduced BRAF V600E IHC test specificity from 99% to 96%. Cautious evaluation of heterogeneous BRAF V600E IHC expression is warranted and comparison with sequencing results is critical, given its reduced test specificity and positive predictive value for detecting the BRAF V600E mutation.
authors.affiliation: Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Tetzlaff
authors.affiliation: Department of Dermatology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
authors.forename: Penvadee
authors.initials: P
authors.lastname: Pattanaprichakul
authors.affiliation: Department of Surgical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wargo
authors.affiliation: Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Patricia S
authors.initials: PS
authors.lastname: Fox
authors.affiliation: Department of Hematopathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Keyur P
authors.initials: KP
authors.lastname: Patel
authors.affiliation: Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Jeannelyn S
authors.initials: JS
authors.lastname: Estrella
authors.affiliation: Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Russell R
authors.initials: RR
authors.lastname: Broaddus
authors.affiliation: Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Williams
authors.affiliation: Department of Melanoma Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Davies
authors.affiliation: Department of Hematopathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Routbort
authors.affiliation: Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Lazar
authors.affiliation: Department of Melanoma Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Scott E
authors.initials: SE
authors.lastname: Woodman
authors.affiliation: Department of Melanoma Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Wen-Jen
authors.initials: WJ
authors.lastname: Hwu
authors.affiliation: Department of Surgical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Gershenwald
authors.affiliation: Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: Victor G
authors.initials: VG
authors.lastname: Prieto
authors.affiliation: Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030. Electronic address: ctcabala@mdanderson.org.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Torres-Cabala
authors.affiliation: Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030. Electronic address: jlcurry@mdanderson.org.
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Curry
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D004252:DNA Mutational Analysis / Q000379:methods*; D005260:Female; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods*; D008297:Male; D008545:Melanoma / Q000235:genetics*; D008875:Middle Aged; D009154:Mutation; D011237:Predictive Value of Tests; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D015203:Reproducibility of Results
chemical_list: D014408:Biomarkers, Tumor; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf
keywords: BRAF V600E; Immunohistochemistry; Melanoma; Next-generation sequencing; Sensitivity; Specificity