NRAS (Q61R), BRAF (V600E) immunohistochemistry: a concomitant tool for mutation screening in melanomas

Metastatic Nodular Melanoma with Angiosarcomatous Transdifferentiation-A Case Report and Review of the Literature

Diagnosing cutaneous melanomas relies mainly on histopathological analysis, which, in selected cases, can be aided by immunohistochemical evaluation of conventional melanocytic markers. Nevertheless, these malignancies, particularly in metastatic settings, may display divergent differentiation with unusual histological and immunohistochemical features. In this context, we present the case of a 65-year-old male diagnosed with typical superficial spreading melanoma who developed recurrence and metastatic lesions featuring angiosarcomatous differentiation. The diagnosis of the initial tumour and the subsequently dedifferentiated lesions was confirmed by ample immunohistochemical analysis, which included several melanocytic markers, as well as mesenchymal and vascular markers. The recurrent tumour and lymph nodes metastases were completely negative for Melan-A and PRAME, and focally positive for SOX10. Additionally, they also displayed diffuse, intense positivity for CD10 and WT1 and focal positivity for CD99, ERB, and CD31. Thus, the diagnosis of primary cutaneous melanoma with recurrent and metastatic divergent angiosarcomatous differentiation was established. This occurrence is particularly rare and can pose important diagnostic challenges. Therefore, in addition to presenting this highly unusual case, we also performed a comprehensive review of the literature on divergent differentiation in melanomas.

Immunohistochemical detection of cancer genetic abnormalities

New applications of immunohistochemistry (IHC) expand rapidly due to the development of molecular analyses and an increased understanding of molecular biology. IHC becomes much more important as a screening or even a confirmatory test for molecular changes in cancer. The past decades have witnessed the release of many immunohistochemical markers of the new generation. The novel markers have extensively high specificity and sensitivity for the detection of genetic abnormalities. In addition to diagnostic utility, IHC has been validated to be a practical tool in terms of treatments, especially molecular targeted therapy. In this review, we first describe the common alterations of protein IHC staining in human cancer: overexpression, underexpression, or loss of expression and altered staining pattern. Next, we examine the relationship between staining patterns and genetic aberrations regarding both conventional and novel IHC markers. We also mention current mutant-specific and fusion-specific antibodies and their concordance with molecular techniques. We then describe the basic molecular mechanisms from genetic events to corresponding protein expression patterns (membranous, cytoplasmic, or nuclear patterns). Finally, we shortly discuss the applications of immunohistochemistry in molecular targeted therapy. IHC markers can serve as a complementary or companion diagnostic test to provide valuable information for targeted therapy. Moreover, immunohistochemistry is also crucial as a companion diagnostic test in immunotherapy. The increased number of IHC novel antibodies is broadening its application in anti-cancer therapies.

Confirmation of canine acanthomatous ameloblastoma using RAS Q61R immunohistochemical staining of formalin-fixed paraffin-embedded tissues

Differentiating canine acanthomatous ameloblastoma (CAA) from oral squamous cell carcinoma (OSCC) based on routine histopathology can be challenging. We have previously shown that more than 95% of CAAs harbor an HRAS p.Q61R somatic mutation, while OSCCs carry either wild-type alleles or other MAPK pathway activating mutations (e.g., HRAS p.Q61L, BRAF p.V595E). Given that HRAS p.Q61R mutations are highly prevalent in CAA, we hypothesized that a RAS Q61R-specific rabbit monoclonal antibody may be a useful tool for confirmation of CAA by immunohistochemical (IHC) staining. In the present study, we assessed IHC staining of archived formalin-fixed and paraffin-embedded biopsy samples with a diagnosis of CAA (n = 23), using a RAS Q61R-specific rabbit monoclonal antibody (SP174) and an automated IHC stainer. Negative control samples consisted of HRAS p.Q61R mutation-negative OSCC tumors with either a known HRAS p.Q61L mutation (n = 1), BRAF p.V595E mutation (n = 4), or wild-type corresponding alleles (n = 3). We found that all 23 CAAs showed diffuse and strong membranous RAS Q61R immunoreactivity (100% sensitivity), while none of the 8 OSCCs showed immunoreactivity (100% specificity). The data supports the use of RAS Q61R-specific rabbit monoclonal antibody for diagnostic IHC confirmation of CAA and ruling out OSCC in dogs.

The Interplay between Tumour Microenvironment Components in Malignant Melanoma

Malignant melanoma has shown an increasing incidence during the last two decades, exhibiting a large spectrum of locations and clinicopathological characteristics. Although current histopathological, biochemical, immunohistochemical, and molecular methods provide a deep insight into its biological behaviour and outcome, melanoma is still an unpredictable disease, with poor outcome. This review of the literature is aimed at updating the knowledge regarding melanoma’s clinicopathological and molecular hallmarks, including its heterogeneity and plasticity, involving cancer stem cells population. A special focus is given on the interplay between different cellular components and their secretion products in melanoma, considering its contribution to tumour progression, invasion, metastasis, recurrences, and resistance to classical therapy. Furthermore, the influences of the specific tumour microenvironment or “inflammasome”, its association with adipose tissue products, including the release of “extracellular vesicles”, and distinct microbiota are currently studied, considering their influences on diagnosis and prognosis. An insight into melanoma’s particular features may reveal new molecular pathways which may be exploited in order to develop innovative therapeutic approaches or tailored therapy.

The Molecular Pathology of Odontogenic Tumors: Expanding the Spectrum of MAPK Pathway Driven Tumors

Odontogenic tumors comprise a heterogeneous group of lesions that arise from the odontogenic apparatus and their remnants. Although the etiopathogenesis of most odontogenic tumors remains unclear, there have been some advances, recently, in the understanding of the genetic basis of specific odontogenic tumors. The mitogen-activated protein kinases/extracellular signal-regulated kinases (MAPK/ERK) pathway is intimately involved in the regulation of important cellular functions, and it is commonly deregulated in several human neoplasms. Molecular analysis performed by different techniques, including direct sequencing, next-generation sequencing, and allele-specific qPCR, have uncovered mutations in genes related to the oncogenic MAPK/ERK signaling pathway in odontogenic tumors. Genetic mutations in this pathway genes have been reported in epithelial and mixed odontogenic tumors, in addition to odontogenic carcinomas and sarcomas. Notably, B-Raf proto-oncogene serine/threonine kinase (BRAF) and KRAS proto-oncogene GTPase (KRAS) pathogenic mutations have been reported in a high proportion of ameloblastomas and adenomatoid odontogenic tumors, respectively. In line with the reports about other neoplasms that harbor a malignant counterpart, the frequency of BRAF p.V600E mutation is higher in ameloblastoma (64% in conventional, 81% in unicystic, and 63% in peripheral) than in ameloblastic carcinoma (35%). The objective of this study was to review MAPK/ERK genetic mutations in benign and malignant odontogenic tumors. Additionally, such genetic alterations were discussed in the context of tumorigenesis, clinical behavior, classification, and future perspectives regarding therapeutic approaches.

Cross-reactivity of NRASQ61R antibody in a subset of Spitz nevi with 11p gain: a potential confounding factor in the era of pathway-based diagnostic approach

The most recent World Health Organization classification for skin tumors (2018) categorizes melanomas and their precursor lesions, benign or intermediate, into nine pathways based not only on their clinical and histomorphologic characteristics but also on their molecular profile and genetic fingerprint. In an index case of a partially sampled atypical spitzoid lesion, which proved to be an 11p-amplified Spitz nevus with HRASQ61R mutation, we observed cross-reactivity with the NRASQ61R antibody (clone SP174). Overall, we assessed the status of HRAS and NRAS genes and their immunoreaction to NRASQ61R antibody in 16 cases of 11p-amplified Spitz nevi/atypical Spitz tumors. We also assessed the immunoexpression of NRASQ61R antibody in various malignancies with proven BRAFV600E, NRASQ61R, L or K, KRASQ61R and HRASQ61R, and HRASQ61R mutations and ALK+ Spitz lesions. Finally, we assessed the expression of PReferentially expressed Antigen in MElanoma (PRAME) immunohistochemistry in our 11p Spitz cohort. Three of 16 cases (3/16) harbored the HRASQ61R mutation and exhibited diffuse immunoreaction with the NRASQ61R antibody. All the cases in our cohort were negative for the NRASQ61R mutation. All NRASQ61R-, KRASQ61R-, and HRASQ61R-mutated neoplasms were positive for the antibody, further supporting the cross-reactivity between the RAS proteins. All the cases of our cohort were essentially negative for PRAME immunohistochemistry. In the era of pathway-based approach in the diagnosis of melanocytic neoplasms, the cross-reactivity between the NRASQ61R- and HRASQ61R-mutated proteins can lead to a diagnostic pitfall in the assessment of lesions with spitzoid characteristics.

NRAS Q61R immunohistochemical staining in thyroid pathology: sensitivity, specificity and utility

AIMS

The diagnosis of thyroid neoplasms relies upon the demonstration of histological parameters that can be focal and prone to subjective interpretation. We evaluated the utility of NRAS Q61R immunohistochemistry (IHC) in the diagnosis of thyroid lesions after determining its specificity and sensitivity as a surrogate marker for RAS Q61R mutation.

METHOD AND RESULTS

NRAS Q61R IHC was performed on 282 primary or metastatic thyroid lesions from 256 patients. RAS mutation status was collected from patients' charts. Sensitivity and specificity of NRAS Q61R IHC for detecting a RAS Q61R mutation was calculated. IHC-positive cases were reviewed to determine the diagnostic utility of NRAS Q61R IHC. NRAS Q61R immunopositivity was seen in non-neoplastic, benign and malignant thyroid lesions. NRAS Q61R antibody cross-reactivity led to the detection of NRAS Q61R, KRAS Q61R and HRAS Q61R proteins. Among primary thyroid carcinomas, immunopositivity was most frequent in papillary thyroid carcinomas, follicular variant (48.0%). The sensitivity and specificity of NRAS Q61R IHC in detecting RAS Q61R mutation was 90.6% and 92.3%, respectively. When positive, the NRAS Q61R stain was determined to be helpful in demonstrating infiltration, tumour size, capsular and/or vascular invasion and multifocality.

CONCLUSION

NRAS Q61R IHC is highly sensitive and specific for the detection of RAS Q61R mutations in thyroid pathology and is particularly relevant in follicular-patterned neoplasms. When evaluated alongside histological features, NRAS Q61R immunoreactivity can be instrumental in the diagnosis and classification of thyroid nodules.

The Current State of Molecular Testing in the BRAF-Mutated Melanoma Landscape

The incidence of melanoma, among the most lethal cancers, is widespread and increasing. Metastatic melanoma has a poor prognosis, representing about 90% of skin cancer mortality. The increased knowledge of tumor biology and the greater understanding of the immune system role in the anti-tumor response has allowed us to develop a more rational approach to systemic therapies. The discovery of activating BRAF mutations in half of all melanomas has led to the development of molecularly targeted therapy with BRAF and MEK inhibitors, which dramatically improved outcomes of patients with stage IV BRAF-mutant melanoma. More recently, the results of clinical phase III studies conducted in the adjuvant setting led to the combined administration of BRAF and MEK inhibitors also in patients with resected high-risk melanoma (stage III). Therefore, BRAF mutation testing has become a priority to determine the oncologist's choice and course of therapy. In this review, we will report the molecular biology-based strategies used for BRAF mutation detection with the main advantages and disadvantages of the most commonly used diagnostic strategies. The timing of such molecular assessment in patients with cutaneous melanoma will be discussed, and we will also examine considerations and approaches for accurate and effective BRAF testing.

Integrating Next-Generation Sequencing with Morphology Improves Prognostic and Biologic Classification of Spitz Neoplasms

The newest World Health Organization classification of skin tumors suggests the elimination of cases with BRAF and NRAS mutations from the categories of Spitz tumors (ST) and Spitz melanoma (SM). The objective of this study is to better characterize the genomics of Spitz neoplasms and assess whether the integration of genomic data with morphologic diagnosis improves classification and prognostication. We performed DNA and RNA sequencing on 80 STs, 26 SMs, and 22 melanomas with Spitzoid features (MSF). Next-generation sequencing data were used to reclassify tumors by moving BRAF and/or NRAS mutated cases to MSF. In total, 81% of STs harbored kinase fusions and/or truncations. Of SMs, 77% had fusions and/or truncations with eight involving MAP3K8. Previously unreported fusions identified were MYO5A-FGFR1, MYO5A-ERBB4, and PRKDC-CTNNB1. The majority of MSFs (84%) had BRAF, NRAS, or NF1 mutations, and 62% had TERT promoter mutations. Only after reclassification, the following was observed: (i) mRNA expression showed distinct clustering of MSF, (ii) six of seven cases with recurrence and all distant metastases were of MSFs, (iii) recurrence-free survival was worse in MSF than in the ST and SM groups (P = 0.0073); and (iv) classification incorporating genomic data was highly predictive of recurrence (OR 13.20, P = 0.0197). The majority of STs and SMs have kinase fusions as primary initiating genomic events. The elimination of BRAF and/or NRAS mutated neoplasms from these categories results in the improved classification and prognostication of melanocytic neoplasms with Spitzoid cytomorphology.

Immunohistochemistry as a Genetic Surrogate in Dermatopathology: Pearls and Pitfalls

Immunohistochemistry (IHC) is routinely performed in most laboratories, and other than purchase of commercially available antibodies, requires no additional equipment or reagents. As such, IHC is an accessible and relatively inexpensive test and one that can be performed quite quickly. This is in sharp contrast to genomic or mutational testing methodologies that are routinely "send out" tests as they require specialized equipment and reagents as well as individuals with expertise in the performance of the tests and analysis of the results, resulting in a prolonged turn-round-time and enhanced associated costs. However, many open questions remain in a rapidly changing therapeutic and scientific landscape with most obvious one being what exactly is the utility of "good old fashioned" IHC in the age of targeted therapy? For molecular applications, is a negative immunohistochemical result enough as a stand-alone diagnostic or predictive product? Is a positive immunohistochemical result perhaps more suitable for a role in screening for molecular alterations rather than a definitive testing modality? This review is an attempt to answer those very questions. We elucidate the broad range of entities in which IHC is currently used as a molecular surrogate and underscore pearls and pitfalls associated with each. Special attention is given to entities for which targeted therapies are currently available and to entities in which molecular data is of clinical utility as a prognosticator.

SP174 Antibody Lacks Specificity for NRAS Q61R and Cross-Reacts With HRAS and KRAS Q61R Mutant Proteins in Malignant Melanoma

HRAS, KRAS, and NRAS, highly homologous proteins, are often mutationally activated in cancer. Usually, mutations cluster in codons 12, 13, and 61 and are detected by molecular genetic testing of tumor DNA. Recently, immunohistochemistry with SP174 antibody has been introduced to detect NRAS Q61R-mutant protein. Studies on malignant melanomas showed that such an approach could be a viable alternative to molecular genetic testing. This investigation was undertaken to evaluate the value of SP174 immunohistochemistry for detection of NRAS Q61R-mutant isoform. Two hundred ninety-two malignant melanomas were evaluated using Leica Bond-Max automated immunostainer. Twenty-nine tumors (10%) showed positive immunoreactivity. NRAS codon 61 was polymerase chain reaction amplified and sequenced in 24 positive and 92 negative cases using Sanger sequencing, quantitative polymerase chain reaction, and next-generation sequencing approaches. A c.182A>G substitution leading to NRAS Q61R mutation was identified in 22 tumors. Two NRAS wild-type tumors revealed c.182A>G substitutions in HRAS and KRAS codon 61, respectively. Both mutations were detected by next-generation sequencing and independently confirmed by Sanger sequencing. None of 85 NRAS codon 61 wild-type tumors and 7 NRAS mutants other than Q61R showed immunoreactivity with SP174 antibody. Thus, SP174 antibody was 100% sensitive in detecting NRAS Q61R-mutant isoform in malignant melanoma, but not fully specific as it cross-reacted with HRAS and KRAS Q61R-mutant proteins. Therefore, molecular testing is needed to determine which RAS gene is mutated. The rarity of HRAS and KRAS Q61R mutants in malignant melanoma let previous investigations erroneously conclude that SP174 is specific for NRAS Q61R-mutant protein.

SP174, NRAS Q61R Mutant-Specific Antibody, Cross-Reacts With KRAS Q61R Mutant Protein in Colorectal Carcinoma

CONTEXT

- NRAS is a member of the RAS family oncoproteins implicated in cancer. Gain-of-function NRAS mutations were reported in a subset of colorectal cancers. These mutations occur at codons 12, 13, and 61 and are detected by molecular genetic testing. Recently, an antibody (clone SP174) became available to immunohistochemically pinpoint NRAS Q61R mutant protein. In malignant melanoma, NRAS Q61R mutant-specific immunohistochemistry was shown to be a valuable supplement to traditional genetic testing.

OBJECTIVE

- To evaluate the significance of NRAS Q61R mutant-specific immunohistochemistry in a cohort of colorectal carcinomas.

DESIGN

- A total of 1185 colorectal carcinomas were immunohistochemically evaluated with SP174 antibody. NRAS Q61R mutant-specific immunohistochemistry was validated by molecular genetic testing including Sanger sequencing, quantitative polymerase chain reaction (qPCR), and next-generation sequencing.

RESULTS

- Twelve tumors showed strong SP174 immunoreactivity. Sanger sequencing detected an identical c.182A>G substitution, causing NRAS Q61R mutation at the protein level, only in 8 SP174-positive cases. These results were confirmed by qPCR study. Subsequently, NRAS wild-type tumors with strong SP174 staining were evaluated by next-generation sequencing and revealed KRAS c.182A>G substitutions predicted to cause KRAS Q61R mutation. Review of colorectal carcinomas with known KRAS and NRAS genotype revealed that none of 62 wild-type tumors or 47 mutants other than Q61R were SP174 positive.

CONCLUSION

- SP174 immunohistochemistry allows sensitive detection of NRAS and KRAS Q61R mutants. However, molecular genetic testing is necessary to determine specifically which RAS gene is mutated.

Distribution bias analysis of germline and somatic single-nucleotide variations that impact protein functional site and neighboring amino acids

Single nucleotide variations (SNVs) can result in loss or gain of protein functional sites. We analyzed the effects of SNVs on enzyme active sites, ligand binding sites, and various types of post translational modification (PTM) sites. We found that, for most types of protein functional sites, the SNV pattern differs between germline and somatic mutations as well as between synonymous and non-synonymous mutations. From a total of 51,138 protein functional site affecting SNVs (pfsSNVs), a pan-cancer analysis revealed 142 somatic pfsSNVs in five or more cancer types. By leveraging patient information for somatic pfsSNVs, we identified 17 loss of functional site SNVs and 60 gain of functional site SNVs which are significantly enriched in patients with specific cancer types. Of the key pfsSNVs identified in our analysis above, we highlight 132 key pfsSNVs within 17 genes that are found in well-established cancer associated gene lists. For illustrating how key pfsSNVs can be prioritized further, we provide a use case where we performed survival analysis showing that a loss of phosphorylation site pfsSNV at position 105 in MEF2A is significantly associated with decreased pancreatic cancer patient survival rate. These 132 pfsSNVs can be used in developing genetic testing pipelines.

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.

BRAF(V600E) and NRAS(Q61L/Q61R) mutation analysis in metastatic melanoma using immunohistochemistry: a study of 754 cases highlighting potential pitfalls and guidelines for interpretation and reporting

BACKGROUND AND AIMS

BRAF or NRAS mutations occur in approximately 60% of cutaneous melanomas, and the identification of such mutations underpins the appropriate selection of patients who may benefit from BRAF and MEK inhibitor targeted therapies. The utility of immunohistochemistry (IHC) to detect NRAS(Q61L) mutations is currently unknown. This study sought to assess the sensitivity and specificity of anti-BRAF(V600E) (VE1), anti-NRAS(Q61R) (SP174) and anti-NRAS(Q61L) (26193) antibodies for mutation detection in a large series of cases.

METHODS AND RESULTS

Mutation status was determined using the OncoCarta assay in 754 cutaneous melanomas. IHC with the anti-BRAF(V600E) antibody was performed in all cases, and the anti-NRAS(Q61R) and anti-NRAS(Q61L) antibodies were assessed in a subset of 302 samples utilizing tissue microarrays. The staining with the anti-BRAF(V600E) and anti-NRAS(Q61R) antibodies was diffuse, homogeneous and cytoplasmic. The anti-NRAS(Q61L) antibody displayed variable intensity staining, ranging from weak to strong in NRAS(Q61L) mutant tumours. The sensitivity and specificity for anti-BRAF(V600E) was 100 and 99.3%, anti-NRAS(Q61R) was 100 and 100% and anti-NRAS(Q61L) was 82.6 and 96.2%, respectively.

CONCLUSIONS

The use of IHC is a fast, efficient and cost-effective method to identify single specific mutations in melanoma patients. BRAF(V600E) and NRAS(Q61R) antibodies have high sensitivity and specificity; however, the NRAS(Q61L) antibody appears less sensitive. IHC can help to facilitate the timely, appropriate selection and treatment of metastatic melanoma patients with targeted therapies. Detection of melanoma-associated mutations by IHC may also provide evidence for a diagnosis of melanoma in metastatic undifferentiated neoplasms lacking expression of melanoma antigens.

Detection of BRAF Mutations Using a Fully Automated Platform and Comparison with High Resolution Melting, Real-Time Allele Specific Amplification, Immunohistochemistry and Next Generation Sequencing Assays, for Patients with Metastatic Melanoma

BACKGROUND

Metastatic melanoma is a severe disease with one of the highest mortality rate in skin diseases. Overall survival has significantly improved with immunotherapy and targeted therapies. Kinase inhibitors targeting BRAF V600 showed promising results. BRAF genotyping is mandatory for the prescription of anti-BRAF therapies.

METHODS

Fifty-nine formalin-fixed paraffin-embedded melanoma samples were assessed using High-Resolution-Melting (HRM) PCR, Real-time allele-specific amplification (RT-ASA) PCR, Next generation sequencing (NGS), immunohistochemistry (IHC) and the fully-automated molecular diagnostics platform IdyllaTM. Sensitivity, specificity, positive predictive value and negative predictive value were calculated using NGS as the reference standard to compare the different assays.

RESULTS

BRAF mutations were found in 28(47.5%), 29(49.2%), 31(52.5%), 29(49.2%) and 27(45.8%) samples with HRM, RT-ASA, NGS, IdyllaTM and IHC respectively. Twenty-six (81.2%) samples were found bearing a c.1799T>A (p.Val600Glu) mutation, three (9.4%) with a c.1798_1799delinsAA (p.Val600Lys) mutation and one with c.1789_1790delinsTC (p.Leu597Ser) mutation. Two samples were found bearing complex mutations.

CONCLUSIONS

HRM appears the less sensitive assay for the detection of BRAF V600 mutations. The RT-ASA, IdyllaTM and IHC assays are suitable for routine molecular diagnostics aiming at the prescription of anti-BRAF therapies. IdyllaTM assay is fully-automated and requires less than 2 minutes for samples preparation and is the fastest of the tested assays.

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.

BRAFV600E mutation in the diagnosis of unicystic ameloblastoma

BACKGROUND

Unicystic ameloblastoma, an odontogenic neoplasm, presents clinical and radiographic similarities with dentigerous and radicular cysts, non-neoplastic lesions. It is not always possible to reach a final diagnosis with the incisional biopsy, leading to inappropriate treatment. The BRAFV600E activating mutation has been reported in a high proportion of ameloblastomas. The purpose of the study was to assess the utility of the detection of the BRAFV600E mutation in the differential diagnosis of unicystic ameloblastoma with dentigerous and radicular cysts.

METHODS

Twenty-six archival samples were included, comprising eight unicystic ameloblastomas (UAs), nine dentigerous and nine radicular cysts. The mutation was assessed in all samples by anti-BRAFV600E (clone VE1) immunohistochemistry (IHC) and by TaqMan mutation detection qPCR assay. Sanger sequencing was further carried out when samples showed conflicting results in the IHC and qPCR.

RESULTS

Although all UAs (8/8) showed positive uniform BRAFV600E staining along the epithelial lining length, the mutation was not confirmed by qPCR and Sanger sequencing in three samples. Positive staining for the BRAFV600E protein was observed in one dentigerous cyst, but it was not confirmed by the molecular methods. Furthermore, 2/9 dentigerous cysts and 2/9 radicular cysts showed non-specific immunostaining of the epithelium or plasma cells. None of the dentigerous or radicular cysts cases presented the BRAFV600E mutation in the qPCR assay.

CONCLUSIONS

The BRAFV600E antibody (clone VE1) IHC may show non-specific staining, but molecular assays may be useful for the diagnosis of unicystic ameloblastoma, in conjunction with clinical, radiological and histopathological features.

BRAF-V600E expression in primary nodular melanoma is associated with aggressive tumour features and reduced survival

BACKGROUND

Around 50% of primary melanomas harbour BRAF mutations, but their prognostic impact has not been clear. Recently, a BRAF-V600E mutation-specific antibody has become available for immunohistochemistry. Here, we investigated for the first time the prognostic impact of BRAF-V600E protein expression in primary melanoma.

METHODS

In a patient series of 248 nodular melanomas, BRAF-V600E and total BRAF expression were assessed by immunohistochemistry using tissue microarray sections of paraffin-embedded archival tissue. Mutation status was assessed by real-time PCR in cases with sufficient tumour tissue (n=191).

RESULTS

Positive BRAF-V600E expression was present in 86 (35%) of the cases, and was significantly associated with increased tumour thickness, presence of tumour ulceration and reduced survival. Further, BRAF-V600E expression was an independent prognostic factor by multivariate analysis, whereas BRAF mutation status was not significant. There was 88% concordance between BRAF-V600E expression and mutation status.

CONCLUSIONS

Our findings indicate that BRAF-V600E expression is a novel prognostic marker in primary melanoma.