Why and how immunohistochemistry should now be used to screen for the BRAFV600E status in metastatic melanoma? The experience of a single institution (LCEP, Nice, France)

Principles of Analytic Validation of Immunohistochemical Assays: Guideline Update

CONTEXT.—

In 2014, the College of American Pathologists developed an evidence-based guideline to address analytic validation of immunohistochemical assays. Fourteen recommendations were offered. Per the National Academy of Medicine standards for developing trustworthy guidelines, guidelines should be updated when new evidence suggests modifications.

OBJECTIVE.—

To assess evidence published since the release of the original guideline and develop updated evidence-based recommendations.

DESIGN.—

The College of American Pathologists convened an expert panel to perform a systematic review of the literature and update the original guideline recommendations using the Grading of Recommendations Assessment, Development and Evaluation approach.

RESULTS.—

Two strong recommendations, 1 conditional recommendation, and 12 good practice statements are offered in this updated guideline. They address analytic validation or verification of predictive and nonpredictive assays, and recommended revalidation procedures following changes in assay conditions.

CONCLUSIONS.—

While many of the original guideline statements remain similar, new recommendations address analytic validation of assays with distinct scoring systems, such as programmed death receptor-1 and analytic verification of US Food and Drug Administration approved/cleared assays; more specific guidance is offered for validating immunohistochemistry performed on cytology specimens.

Comparison of Two Rapid Assays for the Detection of BRAF V600 Mutations in Metastatic Melanoma including Positive Sentinel Lymph Nodes

Testing for the BRAF mutation is mandatory for the management of patients with locally advanced or metastatic melanoma. Molecular analysis based on DNA sequencing remains the gold-standard method for the screening of the different BRAF mutations. These methods must be rapid, sensitive, and specific enough to allow optimal therapeutic management in daily practice and also to include patients in clinical trials. Here, we compared the Idylla BRAF Mutation Test and the anti-BRAF V600E (clone VE1) immunohistochemistry (IHC) in 90 melanoma samples, with a focus on a challenging cohort of 32 positive sentinel lymph nodes. The BRAF status was assessed with both methods independently of the percentage of tumor cells. The concordance rate was calculated excluding both non-contributory analyses and BRAFV600K/R/M mutants due to the specific V600E-IHC test design. The incidence of the BRAFV600E mutation was 33% with both BRAF Idylla and BRAF IHC. The agreement rate was 91% (72/79). Although the agreement rate was high, we suggest that the use of IHC is more suitable for rapid BRAF testing on sentinel lymph node biopsies when associated with a low percentage and scattered tumor cells, which gave a high risk of non-contributory analysis and/or false negative results with the Idylla^TMBRAF Mutation Test.

PD-L1 Expression in 65 Conjunctival Melanomas and Its Association with Clinical Outcome

Conjunctival melanoma (CM) iss a rare and aggressive tumour that is increasing in frequency. The prognostic value of PD-L1 expression, alone or in combination with CD8 and PD-1 expression and the BRAF and NRAS status, has not been determined in CM to date. We evaluated the expression of PD-L1, CD8, PD-1 in CM and investigated whether there was an association between the expression of these markers and the BRAF and NRAS molecular profile as well as some clinico-pathological criteria. A total of sixty-five CM were assessed for PD-L1, PD-1, and CD8 expression by immunohistochemistry (IHC) and for BRAF and NRAS genomic alterations using molecular biology techniques and anti-BRAF and anti-NRAS antibodies. PD-L1 expression in tumour cells (TC) was very low or absent but detected in tumour-infiltrating immune cells (IC). A correlation was observed between the expression of PD-L1, CD8, and PD-1 in IC. No correlation between PD-L1 expression (in tumour and/or immune cells) and BRAF or NRAS mutations was observed. PD-L1 expression in IC correlated with a higher pTNM stage and PD-L1 expression in TC with worse disease-specific survival. PD-L1 expression is a potential prognostic biomarker that correlates with poor prognosis in CM patients.

Molecular and immunohistochemical analysis of BRAF gene in primary cutaneous melanoma: Discovery of novel mutations

BACKGROUND

Determination of BRAF status is mandatory for targeted therapy but it is not currently available in most developing countries.

AIM

We aimed to analyze BRAF mutations in a series of cutaneous melanoma of Tunisian patients and to compare BRAF V600E mutation detection by immunohistochemistry to DNA sequencing.

PATIENTS AND METHODS

Archival formalin fixed paraffin embedded tissues from 28 patients with primary cutaneous melanoma were evaluated for the BRAF mutations by Sanger sequencing and immunohistochemistry.

RESULTS

BRAF mutations were detected in 19/28 (68%) of analyzed tumors. The sensitivity and specificity of immunohistochemistry compared to DNA sequencing for identification of the BRAF V600E mutation were 100%. We found five novel mutations, one of them had deleterious effect.

CONCLUSION

The present study shows an intermediate frequency of mutations of the BRAF gene in cutaneous melanoma of Tunisian patients, and supports the use of immunohistochemistry as a screening test for the assessment of the BRAF V600E status in the management of melanoma in clinical practice.

Prognostic Role of BRAFV600E Cellular Localization in Melanoma

BACKGROUND

Approximately half of cutaneous melanoma tissues harbor BRAF^V600E mutations, resulting in a constitutive activation of the mitogen-activated protein kinase (MAPK) pathway. Nuclear-cytoplasmic transport machinery is dysregulated in neoplastic cells and alters the key regulatory proteins that can lead to tumor progression and drug resistance. The significance of nuclear localization of BRAF^V600E has not been fully understood. We examined the clinical significance of intracellular localization of BRAF^V600E in cutaneous melanoma.

STUDY DESIGN

Immunohistochemical analysis of BRAF^V600E was performed on formalin-fixed, paraffin-embedded specimens of cutaneous melanoma (n = 91). Staining intensity was graded in a blinded manner. Correlations to clinical factors were analyzed by Fisher's exact test and 2-tailed t-test. Localization of BRAF^V600E was determined in melanoma cells, and we investigated their resistance to BRAF^V600E-specific inhibitor according to nuclear localization in both in vitro and in vivo models.

RESULTS

We included 91 patients, of whom 32% (29 of 91) had cytoplasmic BRAF^V600E. Nuclear BRAF^V600E was observed in 30% (27 of 91). Overall, BRAF^V600E expression correlated with TNM stage (p = 0.011), mitotic activity (p = 0.010), and ulceration (p = 0.045). Nuclear BRAF^V600E expression correlated with overall clinical stage (p < 0.001), tumor size (p < 0.001), regional lymph node (p < 0.017), depth of invasion (p = 0.005), Clark level (p < 0.001), mitotic activity (p < 0.001), ulceration (p < 0.001), and margin status (p = 0.017). On a cellular level, BRAF^V600E was identified in the nucleus, and its translocation was serum dependent. Our in vitro and in vivo data revealed sequestration of BRAF^V600E in the cytosol-sensitized resistant cells to vemurafenib; nuclear retention of BRAF^V600E was associated with aggressiveness and drug resistance.

CONCLUSIONS

Nuclear localization of BRAF^V600E is associated with melanoma aggressiveness. Further multi-institutional studies are warranted to confirm the clinical relevance of nuclear localization of BRAF^V600E.

[Immunohistochemistry using clone VE1 is an economic, specific and sensitive method for detecting the presence of BRAFV600E mutations in melanoma]

BACKGROUND

Determination of BRAF mutation status is mandatory in the management of patients with inoperable stage IIIC or stage IV melanoma. Currently, molecular biology (MB) has been validated for detecting the presence of BRAF mutations.

OBJECTIVE

To compare the sensitivity, specificity and cost of immunohistochemistry (IHC) (clone VE1) versus BM methods (qPCR and Sanger sequencing).

PATIENTS AND METHODS

All the samples for which BRAF mutation status was requested between March 2013 and February 2015 at the cellular and molecular analysis laboratory of the Angers Hospital were included retrospectively and consecutively. The IHC (clone VE1) and BM analyses were performed with the same formalin-fixed paraffin embedded tumour samples. The cost of these two methods was determined on the basis of the cost for the French Health Insurance.

RESULTS

Two hundred and seven samples were subjected to a determination of BRAF mutational status in IHC and BM. Only one sample was discordant between these two methods (positive in IHC, negative in BM). The sensitivity and specificity of the IHC was 100% and 99.25% respectively. The ratio of the cost of IHC/BM testing was 1:2.1.

CONCLUSION

IHC (clone VE1) is a specific, sensitive and economic method for determining BRAFV600E mutation status. Nevertheless, this method must be validated in order to be integrated into a decisional algorithm, alongside BM methods, to determine whether targeted BRAF-inhibitor therapy is indicated.

Reflectance confocal microscopy features of BRAF V600E mutated thin melanomas detected by immunohistochemistry

The classification of melanoma into four histological subtypes has been questioned regarding its clinical validity in providing relevant information for treatment for metastatic tumors. Specific genetic alterations are associated with particular clinical and histopathological features, suggesting that these could be helpful in refining existing melanoma classification schemes. We analyzed BRAF V600E mutated melanomas to explore the Reflectance confocal microscopy (RCM) utility as a screening aid in the evaluation of the most appropriate patients for genetic testing. Thus, 32 melanomas were assessed regarding their BRAF V600E mutational status. Experts blinded to dermoscopic images and V600E immunohistochemistry results evaluated RCM images regarding previously described melanoma features. BRAF positive melanomas were related to younger age (p = 0.035), invasive melanomas (p = 0.03) and to the presence of hiporreflective cells (p = 0.02), epidermal nests (p = 0.02), dermal-epidermal junction nests (p = 0.05), edged papillae (p = 0.05), and bright dots (p = 0.05), and to absence of junctional thickening due to isolated cells (p = 0.01) and meshwork (p = 0.02). This study can not characterize other mutations in the BRAF, because the immunohistochemistry is specific to the type V600E. The findings should encourage the genetic evaluation of BRAF mutation. This study highlights the potential of RCM as a supplementary tool in the screening of BRAF-mutated melanomas.

BRAF V600 mutation detection in melanoma: a comparison of two laboratory testing methods

Aims

The assessment of B-raf proto-oncogene, serine/threonine kinase (BRAF) gene status is now standard practice in patients diagnosed with metastatic melanoma with its presence predicting a clinical response to treatment with BRAF inhibitors. The gold standard in determining BRAF status is currently by DNA-based methods. More recently, a BRAF V600E antibody has been developed. We aim to investigate whether immunohistochemical detection of BRAF mutation is a suitable alternative to molecular testing by polymerase chain reaction (PCR).

Methods

We assessed the incidence of BRAF mutation in our cohort of 132 patients, as determined by PCR, as well as examining clinical and histopathological features. We investigated the sensitivity and specificity of the anti-BRAF V600E VE1 clone antibody in detecting the presence of the BRAF V600E mutation in 122 cases deemed suitable for testing.

Results

The incidence of BRAF mutation in our cohort was 28.8% (38/132). Patients with the BRAF mutation were found to be significantly younger at age of diagnosis. BRAF-mutated melanomas tended to be thinner and more mitotically active. The antibody showed a sensitivity of 86.1% with a specificity of 96.9%. The positive predictive value was 96.9%; the negative predictive value was 94.4%. The concordance rate between PCR and immunohistochemical BRAF status was 95.1% (116/122).

Conclusions

The rate of BRAF mutation in our cohort (28.8%) was lower than international published rates of 40%–60%. This may reflect ethnic or geographic differences within population cohorts. The high concordance rate of PCR and immunohistochemical methods in determining BRAF status suggests that immunohistochemistry is potentially a viable, cost-effective alternative to PCR testing and suitable as a screening test for the BRAF mutation.

Is immunohistochemistry of BRAF V600E useful as a screening tool and during progression disease of melanoma patients?

BACKGROUND

In clinical practice the gold standard method to assess BRAF status in patients with metastatic melanoma is based on molecular assays. Recently, a mutation-specific monoclonal antibody (VE1), which detects the BRAF V600E mutated protein, has been developed. With this study we aimed to confirm the clinical value of the VE1 Ventana® antibody, as today a univocal validated and accredited immunohistochemical procedure does not exist, to preliminary detect BRAF status in our routine diagnostic procedures. Moreover, we explored the biological meaning of BRAF immunohistochemical labeling both as a predictor marker of response to target therapy and, for the first time, as a player of acquired tumor drug resistance.

METHODS

We analyzed a retrospective series of 64 metastatic melanoma samples, previously investigated for molecular BRAF status, using a fully automatized immunohistochemical method. We correlated the data to the clinicopathologic characteristics of patients and their clinical outcome.

RESULTS

The sensitivity and the specificity of the Ventana® VE1 antibody were 89.2 and 96.2% respectively, while the positive predictive value and negative predictive value were 97.1 and 86.2%, respectively. For six mutated patients the histological sample before treatment and when disease progressed was available. The immunohistochemical BRAF V600E expression in the specimens when disease progressed was less intense and more heterogeneous compared to the basal expression. Multivariate analysis revealed that a less intense grade of positive expression is an independent predictor of a less aggressive stage at diagnosis (p = 0.0413).

CONCLUSIONS

Our findings encourage the introduction of immunohistochemistry as a rapid screening tool for the assessment of BRAF status in melanoma patients in routine diagnostic procedures and prepare the ground for other studies to highlight the role of immunohistochemical BRAF V600E expression in patients at the time of progression.

Immunohistochemistry as a reliable method for detection of BRAF-V600E mutation in melanoma: a systematic review and meta-analysis of current published literature

BACKGROUND

The BRAF-V600E mutation is associated with tumor aggressiveness and poor prognosis in melanoma patients. Identification of this mutation is clinically important as we now have Food and Drug Administration-approved targeted therapies, such as BRAF and MEK inhibitors, which have been shown to retard disease progression in these patients. Detection of BRAF-V600E by genetic analysis using polymerase chain reaction is the gold standard method for melanoma cases. However, immunohistochemistry (IHC) using a VE1 antibody is rapidly emerging as a trustworthy method for the determination of mutation status in patients' specimens. Our objective in this study was to assess the reliability of IHC compared with genetic methods for successful identification of BRAF-V600E mutation in melanoma tissue specimens.

METHODS

A literature search of PubMed, Web of Science, and Embase was performed for studies comparing IHC with genetic analysis for the detection of BRAF in melanoma patients published through May 28, 2015. Pooled sensitivity, specificity, diagnostic odds ratio, positive, and negative likelihood ratios were calculated using a bivariate model. Logit estimates of sensitivity and specificity with their respective variances were used to plot a hierarchical receiver operating characteristic curve and area under the curve. Heterogeneity was assessed using the Q- and I-squared statistics.

RESULTS

An initial literature search resulted in 287 articles. After two independent reviews and consensus-based discussion to resolve disparities, 21 studies involving a total of 1687 cases met the eligibility criteria and were included in the analysis. The pooled sensitivity of IHC for BRAF-V600E detection was 0.96; 95% confidence interval (CI, 0.94-0.98), specificity 1.00; 95% CI (0.97-1.00), positive likelihood ratio 194.2; 95% CI (37.6-1003.3), negative likelihood ratio 0.04; 95% CI (0.02-0.07), and diagnostic odds ratio 5503 (1199-25,263), as compared with genetic analysis. A high heterogeneity was observed between these studies (Q value of 40.17 & I(2) = 95%; 95% CI (91-99, P < 0.001) which may be explained by studies using different cutoff values for labeling IHC as positive. High accuracy of IHC was depicted by area under the curve in the receiver operating characteristic curve which was 0.99; 95 % CI (0.98-1.00).

CONCLUSIONS

Meta-analysis demonstrates that IHC is highly sensitive and specific for the detection of BRAF-V600E in melanoma cases. IHC is likely to be useful in BRAF mutation detection because it is highly comparable with the genetic methods. Any negative or low staining cases may be selected to undergo genetic analysis based on other clinical and histopathologic features.