Discrepancy between immunohistochemistry and sequencing for BRAF V600E in odontogenic tumours: Comparative analysis of two VE1 antibodies.

Although immunohistochemistry (IHC) along with molecular tests has been investigated in ameloblastoma for BRAF V600E detection, VE1 IHC has not been studied in odontogenic carcinomas (OCs) and benign mixed epithelial and mesenchymal odontogenic tumours (BMOTs). Here, we performed BRAF V600E mutation analysis, examined the expression pattern of VE1 IHC, and comparatively evaluated the performance of two VE1 antibodies in ameloblastomas, OCs and BMOTs. BRAF V600E detection was performed using Sanger sequencing in a total of 47 odontogenic tumours: 28 ameloblastomas, 6 OCs and 13 BMOTs. VE1 IHC was conducted using two different antibodies (IHC-A and IHC-V), and their performance was analysed by calculating the sensitivity and specificity compared with sequencing. BRAF V600E mutations were identified in 24/28 (85.7%) ameloblastomas, 2/5 (40.0%) ameloblastic carcinomas (ACs), 3/7 (42.9%) ameloblastic fibromas and 1/2 (50.0%) ameloblastic fibro-odontomas. In the presence of the mutation, VE1 showed diffuse cytoplasmic staining in ameloblastomas and ACs, whereas all BMOTs were negative for VE1. IHC-A and IHC-V yielded a sensitivity of 76.7% and 60.0%, respectively, although both antibodies showed 100% specificity. OCs and BMOTs have BRAF V600E mutations in common at lower frequencies than ameloblastoma. Diffuse VE1 cytoplasmic staining in AC suggests the utility of MAPK-targeted therapy as selectively applied in ameloblastoma, and consistent VE1 false-negative expression in BMOTs requires further investigation. Considering the high specificity but low sensitivity of VE1 IHC, molecular tests should be performed to determine the presence of BRAF V600E mutations in odontogenic tumours.

Oh KY ，Cho SD ，Yoon HJ ，Lee JI ，Hong SD ... -  《-》

The diagnostic utility of BRAF VE1 mutation-specific immunohistochemistry in ameloblastoma.

Ameloblastoma is a benign, locally aggressive odontogenic neoplasm with variable solid and cystic morphology. On account of its histologic variety, diagnostically challenging cases can bear resemblance to odontogenic keratocyst/keratocystic odontogenic tumor (KCOT) or dentigerous cyst (DC). BRAFV600E mutation has been reported to be specific for and frequent in ameloblastoma, and this study evaluated the usefulness of immunohistochemistry (IHC) using the BRAF VE1 mutant-specific antibody as a diagnostic adjunct in this setting. We investigated 46 ameloblastomas, 30 KCOTs, and 30 DCs. BRAF VE1 IHC was performed on all cases and allele-specific polymerase chain reaction (AS-PCR) for BRAFV600E mutation was performed on 30 ameloblastomas and any IHC-positive KCOT/DC. BRAF VE1 IHC was positive in 31/37 (83.8%) mandibular ameloblastomas but not in any maxillary ameloblastomas (0/9), KCOT (0/30), or DC (0/30). Equivocal staining was seen in 1/37 (3.3%) mandibular ameloblastomas. Of the 30 ameloblastomas subjected to AS-PCR, BRAFV600E mutation was identified in 19/23 (82.6%) mandibular ameloblastomas and 0/7 (0.0%) maxillary ameloblastomas. BRAFV600E mutant ameloblastomas were positive by IHC in 18/19 (94.7%) cases and equivocal in 1/19 (5.3%) cases. All 11 (100.0%) BRAF-wild type ameloblastomas were negative by IHC. BRAF VE1 is an excellent tool for the diagnosis of mandibular ameloblastoma but of limited utility in the maxilla, where it less commonly occurs and where BRAFV600E mutation is considerably less frequent.

Mendez LD ，Wolsefer NS ，Asa SL ，Wasman J ，Yoest JM ，Stojanov IJ ... -  《-》

Assessment of BRAF V600E Status in Colorectal Carcinoma: Tissue-Specific Discordances between Immunohistochemistry and Sequencing.

Although sequencing provides the gold standard for identifying colorectal carcinoma with BRAF V600E mutation, immunohistochemistry (IHC) with the recently developed mouse monoclonal antibody VE1 for BRAF V600E protein has shown promise as a more widely available and rapid method. However, we identified anecdotal discordance between VE1 IHC and sequencing results and therefore analyzed VE1 staining by two different IHC methods (Leica Bond and Ventana BenchMark) in whole tissue sections from 480 colorectal carcinomas (323 BRAF wild-type, 142 BRAF V600E mutation, and 15 BRAF non-V600E mutation). We also compared the results with melanomas and papillary thyroid carcinomas (PTC). With the Bond method, among 142 BRAF V600E-mutated colorectal carcinomas, 77 (54%) had diffuse VE1 staining and 48 (33%) had heterogeneous staining, but 17 (12%) were negative. Among 323 BRAF wild-type colorectal carcinomas, 196 (61%) were negative, but 127 (39%) had staining, including 7 with diffuse staining. When positivity was defined as staining in ≥ 20% of tumor cells, VE1 IHC had sensitivity of 75% and specificity of 93% for BRAF V600E mutation. With the Ventana method, among 57 BRAF V600E-mutated colorectal carcinomas, 36 (63%) had diffuse VE1 staining, whereas 6 (11%) had no or weak (<20% of tumor cells) staining. Among 33 BRAF wild-type colorectal carcinomas, 16 (48%) had no or weak staining, whereas 15 (45%) had heterogeneous staining. In contrast with colorectal carcinoma, Bond and Ventana VE1 IHC in melanoma and PTC were highly concordant with sequencing results. We conclude that VE1 IHC produces suboptimal results in colorectal carcinoma and should not be used to guide patient management.

Estrella JS ，Tetzlaff MT ，Bassett RL Jr ，Patel KP ，Williams MD ，Curry JL ，Rashid A ，Hamilton SR ，Broaddus RR ... -  《-》

Immunohistochemistry with Anti-BRAF V600E (VE1) Mouse Monoclonal Antibody is a Sensitive Method for Detection of the BRAF V600E Mutation in Colon Cancer: Evaluation of 120 Cases with and without KRAS Mutation and Literature Review.

Dvorak K ，Higgins A ，Palting J ，Cohen M ，Brunhoeber P ... -  《-》

[BRAF V600E expression in ameloblastomas, ameloblastic carcinomas and cysts].

Pei J ，Zhang L ，Jia YX ，Chen WH ... -  《-》