Mutation-specific antibody detects mutant BRAFV600E protein expression in human colon carcinomas

Deciphering the Role of BRAFV600E Immunohistochemistry in Breast Lesions: A Comprehensive Review

The BRAFV600E mutation has been extensively studied in various cancers, but its role in breast lesions remains less understood. Immunohistochemistry (IHC) has emerged as a valuable tool for detecting BRAFV600E expression in breast tissue, aiding in diagnosis and prognosis. This comprehensive review examines the significance of BRAFV600E IHC in breast lesions, encompassing its frequency, association with clinicopathological features, and potential clinical implications. We summarize key findings, emphasizing their utility in diagnosis, prognosis prediction, and treatment response assessment. Additionally, we discuss implications for clinical practice, highlighting the need for integrating BRAFV600E IHC into diagnostic algorithms. Recommendations for future research include larger-scale studies to validate findings, optimize detection techniques, and explore therapeutic interventions targeting BRAFV600E in breast cancer. This review contributes to understanding the molecular landscape of breast lesions and informs clinical decision-making in their management.

Prognostic Value of BRAF, Programmed Cell Death 1 (PD1), and PD Ligand 1 (PDL1) Protein Expression in Colon Adenocarcinoma

Patients with colorectal cancer in different stages show variable outcomes/therapeutic responses due to their distinct tumoral biomarkers and biological features. In this sense, this study aimed to explore the prognostic utility of BRAF, programmed death-1 (PD1), and its ligand (PDL1) protein signatures in colon adenocarcinoma. The selected protein markers were explored in 64 archived primary colon adenocarcinomas in relation to clinicopathological features. BRAF overexpression was found in 39% of the cases and was significantly associated with grade 3, N1, advanced Dukes stage, presence of relapse, and shorter overall survival (OS). PD1 expression in the infiltrating immune cells (IICs) exhibited significant association with T2/T3, N0/M0, early Dukes stage, and absence of relapse. PDL1 expression in IICs is significantly associated with advanced nodal stage/distant metastasis, advanced Dukes stage, and shorter OS. Meanwhile, PDL1 expression in neoplastic cells (NC) was associated with the advanced lymph node/Dukes stage. A positive combined expression pattern of PDL1 in NC/IICs was associated with poor prognostic indices. Tumor PDL1 expression can be an independent predictor of OS and DFS. The multivariate analyses revealed that short OS was independently associated with the RT side location of the tumor, PD1 expression in stromal IICs, and PDL1 expression in NC. In conclusion, overexpression of BRAF in colon adenocarcinoma is considered a poor prognostic pathological marker. In addition, PDL1 expression in NC is considered an independent prognostic factor for DFS/OS. Combined immunohistochemical assessment for BRAF and PD1/PDL1 protein expressions in colon adenocarcinoma might be beneficial for selecting patients for future targeted therapy.

BRAF-mutated colorectal adenocarcinomas: pathological heterogeneity and clinical implications

Advances in molecular biology have markedly increased our understanding of the heterogeneous molecular landscape of colorectal cancer (CRC). Up to 15% of CRCs harbor the BRAF p.V600E somatic mutation (BRAFmt), a well-established negative prognostic marker in patients with metastatic CRC (mCRC). The BEACON CRC trial set a new standard of care in patients with progressive BRAFmt cancers, consisting of the combination of encorafenib and cetuximab. On these bases, BRAF mutational testing is now recommended in patients with mCRC. However, efforts are needed to further stratify patients carrying this mutation. Here, we discuss the heterogeneous pathologic and molecular landscape of BRAFmt CRCs, focusing on the promises and pitfalls of molecular diagnostics, on novel biomarkers to improve patients' stratification and on the current diagnostic scenario for CRC. We believe that a better stratification based on histopathological features and novel molecular biomarkers should be performed to optimize patient management and therapeutic decision-making.

Immunohistochemistry in screening for heritable colorectal cancer: what to do with an abnormal result

Recent developments in our understanding of molecular genetics have transformed screening and diagnostic practices for Lynch syndrome. The current standard involves universal tumour analysis of resected colorectal cancer (and ideally polypectomy) specimens using immunohistochemistry and molecular techniques. Patients with abnormal immunohistochemical findings are subsequently referred for definitive mutational testing. This review relates the molecular pathogenesis of Lynch syndrome to current immunohistochemistry-based screening strategies and discusses the interpretation and clinical implications of screening results.

Validation of Immunohistochemistry for the Detection of BRAF V600E-Mutated Lung Adenocarcinomas

BRAF V600E mutation, a missense mutation in exon 15 resulting in valine substitution for glutamate at position 600 within the kinase domain of BRAF oncogene, is found in a subset of lung adenocarcinoma (ADC). The usefulness of immunohistochemistry (IHC) as an alternative diagnostic tool has not been validated. Moreover, the clinical information of patients with BRAF V600E-mutated lung ADC is limited. We retrospectively identified 31 lung ADCs diagnosed with BRAF V600E mutation by standard molecular sequencing methods and reviewed their clinical characteristics and pathological features. An anti-BRAF V600E monoclonal VE1 antibody for IHC was used to confirm the expression patterns. The series was comprised of 99 cases, 29 with BRAF V600E mutation and 70 without BRAF V600E but with other types or undetected mutations. The majority of BRAF V600E-mutated biopsied tissues were poorly differentiated and micropapillary patterns. Application of the IHC VE1 assay was highly feasible in primary/metastatic sites or effusion blocks, yielding positive findings in 28 of 29 (96.6%) BRAF V600E-mutated tumors and negative results in 69 of 70 (98.6%) tumors harboring other types or undetected mutations. Patients who received pemetrexed/platinum-based rather than mutation-targeted chemotherapy as the first-line therapy for metastatic disease showed median overall survival of 15.5 months. Our findings indicated that VE1 antibody-based IHC analysis demonstrated high sensitivity and specificity to detect BRAF V600E-mutated lung ADCs in tissues from primary or metastatic sites.

Correlation of immunohistochemical mismatch repair protein status between colorectal carcinoma endoscopic biopsy and resection specimens

Background

Microsatellite instability is reflective of a deficient mismatch repair system (dMMR), which may be due to either sporadic or germline mutations in the relevant mismatch repair (MMR) gene. MMR status is frequently determined by immunohistochemistry (IHC) for mismatch repair proteins (MMRPs) on colorectal cancer (CRC) resection specimens. However, IHC testing performed on endoscopic biopsy may be as reliable as that performed on surgical resections.

Aim

We aimed to evaluate the reliability of MMR IHC staining on preoperative CRC endoscopic biopsies compared with matched-surgical resection specimens.

Methods

A retrospective search of our institution’s histopathology electronic database was performed. Patients with CRC who had MMR IHC performed on both their preoperative endoscopic biopsy and subsequent resection from January 2010 to January 2016 were included. Concordance of MMR staining between biopsy and resection specimens was assessed.

Results

From 2000 to 2016, 53 patients had MMR IHC performed on both their preoperative colorectal endoscopic biopsy and resection specimens; 10 patients (18.87%) demonstrated loss of ≥1 MMRP on their initial endoscopic tumour biopsy. The remainder (81.13%) showed preservation of staining for all MMRPs. There was complete agreement in MMR IHC status between the preoperative endoscopic biopsies and corresponding resection specimens in all cases (κ=1.000, P<0.000) with a sensitivity of 100% (95% CI 69.15 to 100) and specificity of 100% (95% CI 91.78 to 100) for detection of dMMR.

Conclusion

Endoscopic biopsies are a suitable source of tissue for MMR IHC analysis. This may provide a number of advantages to both patients and clinicians in the management of CRC.

Concomitant KIT/BRAF and PDGFRA/BRAF mutations are rare events in gastrointestinal stromal tumors

AIM

The BRAF mutation is a rare pathogenetic alternative to KIT/PDGFRA mutation in GIST and causes Imatinib resistance. A recent description of KIT and BRAF mutations co-occurring in an untreated GIST has challenged the concept of their being mutually exclusive and may account for ab initio resistance to Imatinib, even in the presence of Imatinib-sensitive KIT mutations. BRAF sequencing is generally limited to KIT/PDGFRA wild-type cases. Hence, the frequency of concomitant mutations may be underestimated.

METHODS

We screened for KIT (exon 9, 11, 13, 17), PDGFRA (exon 12,14, 18) and BRAF (exon 15) mutations a series of 407 GIST. Additionally, we evaluated the BRAF V600E mutation-specific antibody, VE1, as a surrogate for V600E mutation, on a series of 313 GIST (24 on whole sections, 288 cases on tissue array), including 6 cases molecularly ascertained to carry the BRAF V600E mutation.

RESULTS

No concomitant KIT/BRAF or PDGFRA/BRAF mutations were detected. BRAF mutation was detected only in one case, wild-type for KIT/PDGFRA. All the 6 BRAF-mutant cases stained positive with the VE1 antibody. A weak VE1 expression was observed in 14/287 (4.9%) BRAF wild-type cases, as observed also in 2/6 BRAF-mutant cases. Overall in our series, sensitivity and specificity of the VE1 antobody were 100% and 95.1%, respectively.

CONCLUSION

The concomitance of BRAF mutation with either KIT or PDGFRA mutation is rare in GIST. In these tumors, moderate/strong VE1 immunoreactivity is a valuable surrogate for molecular analysis. Instead, genotyping is warranted in the presence of weak VE1 staining.

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

The major aim of this study was to evaluate the performance of anti-BRAF V600E (VE1) antibody in colorectal tumors with and without KRAS mutation. KRAS and BRAF are two major oncogenic drivers of colorectal cancer (CRC) that have been frequently described as mutually exclusive, thus the BRAF V600E mutation is not expected to be present in the cases with KRAS mutation. In addition, a review of 25 studies comparing immunohistochemistry (IHC) using the anti-BRAF V600E (VE1) antibody with BRAF V600E molecular testing in 4041 patient samples was included. One-hundred and twenty cases with/without KRAS or BRAF mutations were acquired. The tissue were immunostained with anti-BRAF V600E (VE1) antibody with OptiView DAB IHC detection kit. The KRAS mutated cases with equivocal immunostaining were further evaluated by Sanger sequencing for BRAF V600E mutation. Thirty cases with BRAF V600E mutation showed unequivocal, diffuse, uniform, positive cytoplasmic staining and 30 cases with wild-type KRAS and BRAF showed negative staining with anti-BRAF V600E (VE1) antibody. Out of 60 cases with KRAS mutation, 56 cases (93.3%) were negative for BRAF V600E mutation by IHC. Four cases showed weak, equivocal, heterogeneous, cytoplasmic staining along with nuclear staining in 25-90% of tumor cells. These cases were confirmed to be negative for BRAF V600E mutation by Sanger sequencing. Overall, IHC with anti-BRAF V600E (VE1) antibody using recommended protocol with OptiView detection is optimal for detection of BRAF V600E mutation in CRC. Our data are consistent with previous reports indicating that KRAS and BRAF V600E mutation are mutually exclusive.

The current value of determining the mismatch repair status of colorectal cancer: A rationale for routine testing

Colorectal Cancer (CRC) is the third most prevalent cancer in men and women. Up to 15% of CRCs display microsatellite instability (MSI). MSI is reflective of a deficient mismatch repair (MMR) system and is most commonly caused by hypermethylation of the MLH1 promoter. However, it may also be due to autosomal dominant constitutional mutations in DNA MMR, termed Lynch Syndrome. MSI may be diagnosed via polymerase chain reaction (PCR) or alternatively, immunohistochemistry (IHC) can identify MMR deficiency (dMMR). Many institutions now advocate universal tumor screening of CRC via either PCR for MSI or IHC for dMMR to guide Lynch Syndrome testing. The association of sporadic MSI with methylation of the MLH1 promoter and an activating BRAF mutation may offer further exclusion criteria for genetic testing. Aside from screening for Lynch syndrome, MMR testing is important because of its prognostic and therapeutic implications. Several studies have shown MSI CRCs exhibit different clinicopathological features and prognosis compared to microsatellite-stable (MSS) CRCs. For example, response to conventional chemotherapy has been reported to be less in MSI tumours. More recently, MSI tumours have been shown to be responsive to immune-checkpoint inhibition providing a novel therapeutic strategy. This provides a rationale for routine testing for MSI or dMMR in CRC.

Immunohistochemistry as a Practical Tool in Molecular Pathology

CONTEXT

-Molecular genetics is playing an increasingly important role in patient care and pathology practice. Immunohistochemistry (IHC) is a valuable and practical tool employed by most pathologists on a regular basis.

OBJECTIVE

-To highlight select examples of how IHC may be used in the realm of molecular diagnostics.

DATA SOURCES

-Select sources on IHC relating to tumor subtyping, hereditary cancer screening, and treatment-response prediction are reviewed. These represent some of the areas in which IHC can be employed by anatomic pathologists to optimize patient care and further inform molecular testing.

CONCLUSION

-In the emerging era of personalized medicine, IHC continues to serve a valuable function, complementing and enhancing other molecular techniques.

Serum and tissue markers in colorectal cancer: State of art

Colorectal cancer (CRC) represents one of the most commonly diagnosed cancers worldwide. It is the second leading cause of cancer death in Western Countries. In the last decade, the survival of patients with metastatic CRC has improved dramatically. Due to the advent of new drugs (irinotecan and oxaliplatin) and target therapies (i.e. bevacizumab, cetuximab, panitumab, aflibercept and regorafenib), the median overall survival has risen from about 12 mo in the mid nineties to 30 mo recently. Molecular studies have recently widened the opportunity for testing new possible markers, but actually, only few markers can be recommended for practical use in clinic. In the next future, the hope is to have a complete panel of clinical biomarkers to use in every setting of CRC disease, and at the same time: 1) to receive information about prognostic significance by their expression and 2) to be oriented in the choice of the adequate treatment. Moreover, molecular analyses have shown that the natural history of all CRCs is not the same. Individual patients with same stage tumors may have different long-term prognosis and response to therapy. In addition, some prognostic variables are likely to be more important than others. Here we review the role of serum and tissue markers according to the recently published English literature. This paper is an extension of the article "Biological and clinical markers in colorectal cancer: state of art" by Cappellani A published in Jan 2010.

Immunohistochemistry with the anti-BRAF V600E (VE1) antibody: impact of pre-analytical conditions and concordance with DNA sequencing in colorectal and papillary thyroid carcinoma

Summary

The most common of all activating BRAF mutations (T1799A) leads to a substitution of valine (V) to glutamic acid (E) at the position 600 of the amino acid sequence. The major goal of this study was to compare detection of the BRAF V600E mutation by DNA sequencing with immunohistochemistry (IHC) using the anti-BRAF V600E (VE1) antibody. Archival formalin fixed, paraffin embedded tissues from 352 patients with colon adenocarcinoma (n = 279) and papillary thyroid carcinoma (n = 73) were evaluated for the BRAF V600E mutation by sequencing and IHC. The discordant cases were re-evaluated by repeat IHC, SNaPshot and next-generation sequencing (NGS). Furthermore, the effect of pre-analytical variables on the utility of this antibody was evaluated in two xenograft mouse models.

After resolving 15 initially discordant cases, 212 cases were negative for the BRAF V600E mutation by IHC. Of these, 210 cases (99.1%) were also negative by sequencing and two cases (0.9%) remained discordant. Of the 140 cases that were IHC positive for BRAF V600E, 138 cases were confirmed by sequencing (98.6%) and two cases remained discordant (1.4%). Overall, the negative predictive value was 99.1%, positive predictive value 98.6%, sensitivity 98.6%, specificity 99.1% and overall percentage agreement 98.9% (348/352 cases). Tissue fixation studies indicated that tissues should be fixed for 12–24 h within 2 h of tissue collection with 10% neutral buffered formalin.

A combination of immunohistochemistry and molecular approaches improves highly sensitive detection of BRAF mutations in papillary thyroid cancer

The optimal method for BRAF mutation detection remains to be determined despite advances in molecular detection techniques. The aim of this study was to compare, against classical Sanger sequencing, the diagnostic performance of two of the most recently developed, highly sensitive methods: BRAF V600E immunohistochemistry (IHC) and peptide nucleic-acid (PNA)-clamp qPCR. BRAF exon 15 mutations were searched in formalin-fixed paraffin-embedded tissues from 86 papillary thyroid carcinoma using the three methods. The limits of detection of Sanger sequencing in borderline or discordant cases were quantified by next generation sequencing. BRAF mutations were found in 74.4 % of cases by PNA, in 71 % of cases by IHC, and in 64 % of cases by Sanger sequencing. Complete concordance for the three methods was observed in 80 % of samples. Better concordance was observed with the combination of two methods, particularly PNA and IHC (59/64) (92 %), while the combination of PNA and Sanger was concordant in 55 cases (86 %). Sensitivity of the three methods was 99 % for PNA, 94.2 % for IHC, and 89.5 % for Sanger. Our data show that IHC could be used as a cost-effective, first-line method for BRAF V600E detection in daily practice, followed by PNA analysis in negative or uninterpretable cases, as the most efficient method. PNA-clamp quantitative PCR is highly sensitive and complementary to IHC as it also recognizes other mutations besides V600E and it is suitable for diagnostic purposes.

Sessile Serrated Polyps are Precursors of Colon Carcinomas With Deficient DNA Mismatch Repair

We investigated whether sessile serrated adenomas/polyps (SSA/Ps) are direct precursors of colorectal carcinomas. We identified colon carcinomas that arose from SSA/Ps among 2646 colorectal cancers included in the surgical pathology database at the Mayo Clinic (2006-2012). Molecular features of the serrated neoplasia pathway were analyzed in these tumors by immunohistochemical analyses of mutant BRAF (V600E) and MLH1 proteins. Among the 33 identified SSA/P-associated colonic adenocarcinomas (median patient age, 75 y), 24 developed in women (73%), 31 were located in the proximal colon (94%), and 23 (69%) were TNM stage I or II. Thirty-one of the tumors (94%) expressed mutant BRAF; of these, 26 also had loss of MLH1 (79%), indicating deficient DNA mismatch repair of sporadic origin. Twenty-two of the tumors (67%) were interval cancers that were more common in women and did not differ significantly in TNM stage, BRAF mutation, or loss of MLH1. By histopathology, SSA/Ps that were associated with colon carcinomas contained frequent dysplasia (48%). Most cancers that arose from SSA/Ps were located on the right side of the colon and had mutant BRAF and loss of MLH1. These findings indicate that SSA/Ps are precursors of most sporadic colon carcinomas with deficient DNA mismatch repair.

Localization of active, dually phosphorylated extracellular signal-regulated kinase 1 and 2 in colorectal cancer with or without activating BRAF and KRAS mutations

Colorectal cancers (CRC) often show activating mutations of the KRAS or BRAF genes, which stimulate the extracellular signal-regulated kinase (ERK) pathway, thus increasing cell proliferation and inhibiting apoptosis. However, immunohistochemical results on ERK activation in such tumors differ greatly. Recently, using a highly optimized immunohistochemical method, we obtained evidence that high levels of ERK activation in rectal adenocarcinomas were associated with resistance to radiochemotherapy. In order to determine whether KRAS and/or BRAF mutations correlate to immunohistochemically detectable increases in phosphorylation of ERK (pERK), we stained biopsies from 36 CRC patients with activating mutations in the BRAF gene (BRAFV600E: BRAF(m)), the KRAS gene (KRAS(m)) or in neither (BRAF/KRAS(n)) with this optimized method. Staining was scored in blind-coded specimens by two observers. Staining of stromal cells was used as a positive control. BRAF(m) or KRAS(m) tumors did not show higher staining scores than BRAF/KRAS(n) tumors. Although BRAFV600E staining occurred in over 90% of cancer cells in all 9 BRAF(m) tumors, 3 only showed staining for pERK in less than 10% of cancer cell nuclei. The same applied to 4 of the 14 KRAS(m) tumors. A phophorylation-insensitive antibody demonstrated that lack of pERK staining did not reflect defect expression of ERK1/2 protein. Thus, increased staining for pERK does not correlate to BRAF or KRAS mutations even with a highly optimized procedure. Further studies are required to determine whether this reflects differences in expression of counterregulatory molecules, including ERK phosphatases.

Validation of a Manual Protocol for BRAF V600E Mutation-specific Immunohistochemistry

Detection of BRAF V600E has diagnostic, prognostic, and therapeutic relevance. The recently developed BRAF V600E mutation-specific antibody has evolved into a feasible alternative to DNA analysis. The plethora of immunohistochemical protocols makes implementation tedious and, here we tested a set of manual and automated protocols and compared test performance with sequencing results. For assays, we employed formalin-fixed, in part decalcified, and paraffin-embedded tissue samples. Empiric testing of manual protocols included 10 variables in 17 protocols. Automated immunohistochemical staining and BRAF pyrosequencing served as independent test methods. Test performance measures were compared without considering 1 method as a standard. Four well-fixed samples (2WT/2Mut) were used for testing of all protocols and indicated 2 correctly classifying procedures. Practical performance assessment employed 33 independent tissue samples, composed of 27 leukemias (by pyrosequencing: 8 wild-type; 18 mutated; 1 noninformative) and 6 melanomas (V600E; V600K; wild-type, 2 each). Manual V600E staining was positive in 20 cases (19 of 20 V600E-containing samples plus the 1 sample that was noninformative), whereas all wild-type and V600K cases were immunonegative. Manual or automated staining as well as pyrosequencing would have missed an equal number of V600E-mutated cases and the correlation coefficient for these methods was 0.75 to 0.93 (substantial to almost perfect); the Youden index was 0.95. Detection of V600E-mutated BRAF at the protein level in routine and decalcified tissue samples is possible, and the presented manual protocols should expedite implementation in routine diagnostic practice. Our results indicate that both molecular techniques should be considered complementary.

Utility of BRAF V600E mutation-specific immunohistochemistry in detecting BRAF V600E-mutated gastrointestinal stromal tumors

OBJECTIVES

As patients with BRAF V600E mutation respond to BRAF inhibitors, it is important to identify these mutations to stratify patients for the appropriate therapy. In this study, we evaluated the utility of a BRAF V600E allele-specific antibody in gastrointestinal stromal tumors (GISTs).

METHODS

BRAF V600E mutation-specific immunohistochemistry (negative, weak, or moderate/strong expression) and BRAF sequencing were performed on 38 consecutive GISTs diagnosed between January 2013 and April 2014.

RESULTS

GISTs from a cohort of 25 men and 13 women (mean age, 61 years; range, 39-88 years) were localized to the stomach (18), small bowel (10), colon (three), rectum (two), and pelvis/omentum (five). Strong and diffuse cytoplasmic BRAF expression was noted in two (5%) of 38 cases, while eight (21%) of 38 cases showed weak staining, and 28 (74%) of 38 cases were negative. Both of the strongly positive cases arose in the stomach, occurring in a 42-year-old and a 47-year-old woman, respectively. The lesions measured 0.8 and 1 cm, showed spindle cell morphology, and had no risk of progressive disease by Miettinen criteria. Both cases showed heterozygous BRAF V600E, while no BRAF mutations were detected in cases with weak or negative BRAF expression.

CONCLUSIONS

BRAF V600E mutation-specific immunohistochemistry is a highly sensitive and specific method for detecting BRAF-mutated GISTs.

Annexin A10 expression in colorectal cancers with emphasis on the serrated neoplasia pathway

AIM: To validate the utility of Annexin A10 as a surrogate marker of the serrated neoplasia pathway in invasive colorectal cancers (CRCs).

METHODS: A total of 1133 primary CRC patients who underwent surgical resection at Seoul National University Hospital between January 2004 and December 2007 were enrolled. Expression of Annexin A10 was evaluated by immunohistochemistry using tissue microarray and paired to our findings on clinicopathologic and molecular characteristics of each individual. CpG island methylator phenotype was determined by MethyLight assay and microsatellite instability was determined by high performance liquid chromatography. KRAS and BRAF mutation status was evaluated by direct sequencing and allele-specific PCR. Univariate and stage-specific survival analyses were performed to reveal the prognostic value of Annexin A10 expression.

RESULTS: Annexin A10 expression was observed in 66 (5.8%) of the 1133 patients. Annexin A10 expression was more commonly found in females and was associated with proximal location, ulcerative gross type, advanced T category, N category and TNM stage. CRCs with Annexin A10 expression showed an absence of luminal necrosis, luminal serration and mucin production. CRCs with Annexin A10 expression were associated with CpG island methylator phenotype, microsatellite instability and BRAF mutation. In survival analysis, Annexin A10 expression was associated with poor overall survival and progression-free survival, especially in stage IV CRCs.

CONCLUSION: Annexin A10 expression is associated with poor clinical behavior and can be used a supportive surrogate marker of the serrated neoplasia pathway in invasive CRCs.

Molecular and immunohistochemical characterization reveals novel BRAF mutations in metanephric adenoma

Metanephric adenoma (MA) is a rare benign renal tumor comprised of a neoplastic proliferation of primitive metanephric tubular cells. A previous study identified BRAF V600E mutations in approximately 90% of MA and found that similar BRAF exon 15 mutations are exceedingly rare in other common renal tumors, including renal cell carcinoma and oncocytoma. A recent follow-up study has validated mutation-specific immunohistochemistry (IHC) for detection of BRAF V600E mutations in a small cohort of MA. Here, we extend these findings to a larger, independent cohort of MA, demonstrating an overall 88% sensitivity and 100% specificity for BRAF V600E IHC. In addition, we report 2 cases of MA with novel BRAF exon 15 mutations, including a V600D missense mutation and a compound V600D and K601L missense mutation. Finally, we evaluate BRAF V600E IHC in a large tissue microarray cohort of common renal tumors and find no significant expression in several renal cell carcinoma subtypes. These data support a role for BRAF V600E IHC in diagnostically challenging cases of MA and expand the spectrum of BRAF exon 15 mutations in this uncommon but unique renal neoplasm.

KRAS and BRAF Mutation Detection: Is Immunohistochemistry a Possible Alternative to Molecular Biology in Colorectal Cancer?

KRAS genotyping is mandatory in metastatic colorectal cancer treatment prior to undertaking antiepidermal growth factor receptor (EGFR) monoclonal antibody therapy. BRAF V600E mutation is often present in colorectal carcinoma with CpG island methylator phenotype and microsatellite instability. Currently, KRAS and BRAF evaluation is based on molecular biology techniques such as SNaPshot or Sanger sequencing. As molecular testing is performed on formalin-fixed paraffin-embedded (FFPE) samples, immunodetection would appear to be an attractive alternative for detecting mutations. Thus, our objective was to assess the validity of KRAS and BRAF immunodetection of mutations compared with the genotyping reference method in colorectal adenocarcinoma. KRAS and BRAF genotyping was assessed by SNaPshot. A rabbit anti-human KRAS polyclonal antibody was tested on 33 FFPE colorectal tumor samples with known KRAS status. Additionally, a mouse anti-human BRAF monoclonal antibody was tested on 30 FFPE tumor samples with known BRAF status. KRAS immunostaining demonstrated both poor sensitivity (27%) and specificity (64%) in detecting KRAS mutation. Conversely, BRAF immunohistochemistry showed perfect sensitivity (100%) and specificity (100%) in detecting V600E mutation. Although molecular biology remains the reference method for detecting KRAS mutation, immunohistochemistry could be an attractive method for detecting BRAF V600E mutation in colorectal cancer.

Application of immunohistochemistry in gastrointestinal and liver neoplasms: new markers and evolving practice

CONTEXT

Diagnosis of primary gastrointestinal and liver neoplasms is usually straightforward. Immunohistochemistry is most helpful to differentiate metastatic carcinomas with morphologic similarity and to resolve tumors of unknown origin. Recently, several new markers highly sensitive and specific for primary liver and gastrointestinal tumors have been discovered. Their potential diagnostic application has not been widely appreciated by general practicing pathologists. In addition, a new trend in immunohistochemistry application has started, focusing on assessing predictive markers (such as human epidermal growth factor receptor 2) and mutation-specific markers (v-raf murine sarcoma viral oncogene homolog B V600E) to directly guide clinical management. Practicing pathologists need to be aware of and prepared for this evolving trend.

OBJECTIVES

To summarize the usefulness of several recently discovered immunohistochemical markers in the study of gastrointestinal and liver tumors; to suggest the most current and effective immunohistochemical panels addressing common diagnostic challenges for these tumors; to share practical experience and useful tips for human epidermal growth factor receptor 2 testing in gastric and gastroesophageal junction adenocarcinoma and v-raf murine sarcoma viral oncogene homolog B V600E immunohistochemistry in colorectal carcinoma.

DATA SOURCES

Sources include literature review, and authors' research data and practice experience. The cases illustrated are selected from the pathology archives of the Geisinger Medical Center (Danville, Pennsylvania).

CONCLUSIONS

Application of immunohistochemistry in gastrointestinal and liver tumors continues to evolve. New tumor-specific markers constantly emerge and help pathologists to further improve diagnostic accuracy. Assessment of predictive and prognostic markers by immunohistochemistry in routine pathologic diagnosis is a new trend and will greatly facilitate the advancement of personalized cancer therapy.

Deficient mismatch repair in colorectal cancer: current perspectives on patient management and future directions

Abstract 

Molecular aberrations leading to colorectal cancer are diverse and heterogeneity exists both at a molecular level and in clinical behavior. Defective mismatch repair (dMMR) is a feature of 15% of colorectal cancers. These are hypermutated tumors, mostly right sided and histopathologically elicit a marked immune response. A proportion of these arise due to germline mutation of a mismatch repair gene giving rise to Lynch syndrome, while the majority arise sporadically due to somatic alteration of the MLH1 mismatch repair gene. Although dMMR is associated with an excellent patient prognosis, as tumor stage advances the frequency of dMMR declines and the association with improved prognosis dissipates. It is apparent that dMMR tumors do not represent a unique molecular subset. As the knowledge of the underlying biology evolves, the hope is for individualized therapy that goes well beyond the crude and oversimplified categorization of dMMR versus proficient MMR.

Current Understanding of BRAF Alterations in Diagnosis, Prognosis, and Therapeutic Targeting in Pediatric Low-Grade Gliomas

The mitogen-activated protein kinase (MAPK) pathway is known to play a key role in the initiation and maintenance of many tumors as well as normal development. This often occurs through mutation of the genes encoding RAS and RAF proteins which are involved in signal transduction in this pathway. BRAF is one of three RAF kinases which act as downstream effectors of growth factor signaling leading to cell cycle progression, proliferation, and survival. Initially reported as a point mutation (V600E) in the majority of metastatic melanomas, other alterations in the BRAF gene have now been reported in a variety of human cancers including papillary thyroid cancer, colon carcinomas, hairy cell leukemia, and more recently in gliomas. The identification of oncogenic mutations in the BRAF gene have led to a revolution in the treatment of metastatic melanoma using targeted molecular therapies that affect the MAPK pathway either directly through BRAF inhibition or downstream through inhibition of MEK. This review describes the molecular biology of BRAF in the context of pediatric low-grade gliomas, the role of BRAF as a diagnostic marker, the prognostic implications of BRAF, and evidence for therapeutic targeting of BRAF.

A modified Lynch syndrome screening algorithm in colon cancer: BRAF immunohistochemistry is efficacious and cost beneficial

OBJECTIVES

Somatic BRAF mutation in colon cancer essentially excludes Lynch syndrome. We compared BRAF V600E immunohistochemistry (IHC) with BRAF mutation in core, biopsy, and whole-section slides to determine whether IHC is similar and to assess the cost-benefit of IHC.

METHODS

Resection cases (2009-2013) with absent MLH1 and PMS2 and prior BRAF mutation polymerase chain reaction results were chosen (n = 57). To mimic biopsy specimens, tissue microarrays (TMAs) were constructed. In addition, available biopsies performed prior to the resection were available in 15 cases. BRAF V600E IHC was performed and graded on TMAs, available biopsy specimens, and whole-section slides. Mutation status was compared with IHC, and cost-benefit analysis was performed.

RESULTS

BRAF V600E IHC was similar in TMAs, biopsy specimens, and whole-section slides, with only four (7%) showing discordance between IHC and mutation status. Using BRAF V600E IHC in our Lynch syndrome screening algorithm, we found a 10% cost savings compared with mutational analysis.

CONCLUSIONS

BRAF V600E IHC was concordant between TMAs, biopsy specimens, and whole-section slides, suggesting biopsy specimens are as useful as whole sections. IHC remained cost beneficial compared with mutational analysis, even though more patients needed additional molecular testing to exclude Lynch syndrome.

BRAF V600E mutation-specific antibody: A review

The significance of BRAF mutations in neoplasia was first recognized in 2002 when mutations were discovered in a broad range of cancers. Numerous subsequent studies expanded our understanding of BRAF V600E as a critical diagnostic, prognostic, and predictive biomarker in many cancers. Additionally, the advent of small-molecule inhibitors of BRAF V600E rendered assessment of BRAF mutation status essential in tumors such as melanoma. In clinical practice, evaluation of BRAF mutation status has routinely been performed by DNA-based assays utilizing polymerase chain reaction (PCR). However, molecular testing is not available at many hospitals since it is time-consuming, expensive, and requires expertise in molecular techniques. The first BRAF V600E-specific antibody was reported in 2011 (clone VE1). A purified version of this antibody as well as a second monoclonal antibody targeted to BRAF V600E is now commercially available. In this review, clinicopathologic characteristics associated with BRAF-mutant tumors will be highlighted, and the prognostic and predictive implications of a BRAF V600E mutation will be discussed with a focus on melanoma, thyroid carcinoma and colorectal carcinoma. Additionally, we will review the correlation between immunohistochemistry and molecular results and deliberate how BRAF immunohistochemistry might be utilized in the evaluation of these tumors.

Evaluation of allele-specific PCR and immunohistochemistry for the detection of BRAF V600E mutations in hairy cell leukemia

OBJECTIVES

Detection of BRAF V600E mutations in hairy cell leukemia (HCL) has important diagnostic utility. In this study, we sought to compare immunohistochemistry with an antibody specific for this mutation to a sensitive molecular assay.

METHODS

The performance of the BRAF V600E-specific VE1 antibody was compared with that of allele-specific polymerase chain reaction (PCR) in 22 formalin-fixed, paraffin-embedded (FFPE) specimens with HCL involvement, along with nine splenic marginal zone lymphomas (SMZLs), 10 follicular lymphomas (FLs), 10 mantle cell lymphomas (MCLs), and 10 chronic lymphocytic leukemia/small lymphocytic lymphomas (CLL/SLLs). An additional 11 SMZLs, 100 FLs, 20 MCLs, 83 CLL/SLL specimens, and 49 reactive tonsils within tissue microarrays were stained with VE1.

RESULTS

A BRAF V600E mutation was detected in 17 (77.3%) of 22 HCL cases by PCR. Immunohistochemistry demonstrated VE1 staining in 20 (90.9%) cases, identifying low-level (~1%) involvement in three HCL cases that were mutation negative by PCR. Evaluation of additional material from these patients confirmed the presence of BRAF V600E. Thirty-nine non-HCL cases were negative by both methods. Within tissue microarrays, weak false-positive staining was observed in two (0.8%) of 263 non-HCL cases.

CONCLUSIONS

VE1 immunohistochemistry is more sensitive than allele-specific PCR in FFPE bone marrow specimens and can be applied to decalcified core biopsy specimens that are not appropriate for molecular techniques.

Immunohistochemistry of colorectal cancer biomarker phosphorylation requires controlled tissue fixation

Phosphorylated signaling molecules are biomarkers of cancer pathophysiology and resistance to therapy, but because phosphoprotein analytes are often labile, poorly controlled clinical laboratory practices could prevent translation of research findings in this area from the bench to the bedside. We therefore compared multiple biomarker and phosphoprotein immunohistochemistry (IHC) results in 23 clinical colorectal carcinoma samples after either a novel, rapid tissue fixation protocol or a standard tissue fixation protocol employed by clinical laboratories, and we also investigated the effect of a defined post-operative "cold" ischemia period on these IHC results. We found that a one-hour cold ischemia interval, allowed by ASCO/CAP guidelines for certain cancer biomarker assays, is highly deleterious to certain phosphoprotein analytes, specifically the phosphorylated epidermal growth factor receptor (pEGFR), but shorter ischemic intervals (less than 17 minutes) facilitate preservation of phosphoproteins. Second, we found that a rapid 4-hour, two temperature, formalin fixation yielded superior staining in several cases with select markers (pEGFR, pBAD, pAKT) compared to a standard overnight room temperature fixation protocol, despite taking less time. These findings indicate that the future research and clinical utilities of phosphoprotein IHC for assessing colorectal carcinoma pathophysiology absolutely depend upon attention to preanalytical factors and rigorously controlled tissue fixation protocols.

BRAF V600E immunohistochemistry is reliable in primary and metastatic colorectal carcinoma regardless of treatment status and shows high intratumoral homogeneity

In colorectal carcinoma the evaluation of BRAF mutation status is increasingly being performed given its utility as a prognostic and predictive biomarker. However, there are conflicting reports of the sensitivity and specificity of BRAF V600E immunohistochemistry (IHC), and little is known about its reliability in tissues collected from metastatic sites or after chemotherapy, radiation therapy and/or targeted therapy. The degree of intratumoral staining heterogeneity is also not well established. We performed IHC for BRAF V600E (VE1) on 204 cases of colorectal carcinoma including 59 with the BRAF V600E mutation. These included primary (n=147) and metastatic/recurrent (n=57) tumors, collected before (n=133) or after (n=71) chemotherapy, radiation therapy and/or targeted therapy. Evaluation of a test cohort (39 cases) with knowledge of mutation status established a specific staining pattern for the mutation: diffuse cytoplasmic staining of near-uniform intensity, regardless of strength of staining. Using this pattern, pathologists at 3 levels of training independently performed blinded evaluation of the remaining cases. BRAF V600E staining was 96.3% sensitive and 98.5% specific for the mutation, including both pretreatment and posttreatment specimens. Fleiss κ for interobserver agreement was 0.96. Staining of whole sections of the BRAF mutants showed diffuse staining in all cases and uniform or near-uniform intensity in 91%. In 20 cases with both pretreatment and posttreatment specimens, there was 100% accuracy and agreement in staining between samples. We conclude that BRAF V600E IHC is reliable for the evaluation of mutational status in colorectal carcinoma regardless of site or prior treatment history, and staining shows a high degree of intratumoral homogeneity.

Select biomarkers for tumors of the gastrointestinal tract: present and future

CONTEXT

Advances in molecular biomarkers of the gastrointestinal tract have contributed to a decline in the incidence of and mortality from diseases of the gastrointestinal tract. The discovery and clinical validation of new biomarkers are important to personalized cancer therapy, and numerous clinical trials are currently ongoing to help identify individualized therapy affecting these biomarkers and molecular mechanisms they represent. Distinct molecular pathways leading to cancers of the colorectum, esophagus, stomach, small bowel, and pancreas have been identified. Using biomarkers in these pathways to direct patient care, including selection of proper molecular testing for identification of actionable mutations and reporting the results of these biomarkers to guide clinicians and genetic counselors, is paramount.

OBJECTIVE

To examine and review select clinically actionable biomarkers of the colon, esophagus, stomach, small bowel, and pancreas, including present and future biomarkers with relevant clinical trials.

DATA SOURCES

Extensive literature review and practical and consultation experience of the authors.

CONCLUSIONS

Although numerous biomarkers have been identified and are currently guiding patient therapy, few have shown evidence of clinical utility in the management of patients with gastrointestinal cancers. Inconsistent results and discordant proposed algorithms for testing were identified throughout the literature; however, the potential for biomarkers to improve outcomes for patients with gastrointestinal cancer remains high. Continued advances through high-quality studies are needed.

Performance comparison of three BRAF V600E detection methods in malignant melanoma and colorectal cancer specimens

Personalized cancer care requires reliable biomarkers. While the BRAF V600E mutation is implemented in the clinic, no method for its detection has so far been established as reference. We aimed to perform a comprehensive comparison of three methods currently being used for V600E detection in clinical samples. We analysed genomic DNA from 127 malignant melanomas (77 patients) and 389 tumours from 141 colorectal cancer patients (383 liver metastases and 6 primary tumours) by Sanger sequencing and a single probe-based high-resolution melting assay (LightMix). Formalin-fixed paraffin-embedded (FFPE) tissue from a subset of these lesions (n = 77 and 304, respectively) was analysed by immunohistochemistry (IHC) using the V600E-specific antibody VE1. In a dilution series of V600E-mutated DNA in wild-type DNA, the detection limit for the LightMix assay was 1:1000 mutated alleles while it was 1:10 for Sanger sequencing. In line with this, we detected 15 additional mutated melanoma samples and two additional mutated metastatic colorectal cancer samples by the LightMix assay compared to Sanger sequencing. For the melanoma samples, we observed high concordance between DNA-based methods and analysis by IHC. However, in colorectal samples, IHC performed poorly with 12 samples being scored as V600E positive exclusively by IHC and nine samples being scored as V600E negative exclusively by IHC. In conclusion, the VE1 antibody is not recommendable for clinical tests of colorectal cancer samples. For melanoma samples, IHC may be useful as a screening tool guiding further analytical approaches.

Detection of the BRAF V600E mutation in colon carcinoma: critical evaluation of the imunohistochemical approach

Recently BRAF V600E mutant-specific antibody (clone VE1) became available to immunohistochemically pinpoint the occurrence of these BRAF-mutant proteins in different tumors, such as colon carcinoma. Detection of BRAF mutations is important for the accurate application of targeted therapy against BRAF serine-threonine kinase activation. In this study, we evaluated 113 colon carcinomas including 95 primary and 27 metastatic tumors with the VE1 antibody using Leica Bond-Max automated immunohistochemistry. To ensure comprehensive BRAF V600E mutation detection, all cases were evaluated using 4 molecular methods (Sanger sequencing, the Cobas 4800 BRAF V600 Mutation Test, BRAF V600 allele-specific polymerase chain reaction, and BRAF V600 quantitative polymerase chain reaction) with nearly 100% concordance. Molecular and immunohistochemical studies were blinded. Furthermore, all cases were evaluated for KRAS and NRAS mutations as parameters mutually exclusive with BRAF mutations offering parallel evidence for BRAF mutation status. Strong to moderate VE1 positivity was seen in 34 tumors. Twelve colon carcinomas showed weak VE1 immunohistochemical staining, and 67 were entirely negative. An identical c.1799T>A single nucleotide substitution leading to the BRAF V600E mutation was identified in 27 of 113 (24%) colon carcinomas. A majority of BRAF-mutant tumors were located in the right side of the colon and had mismatch-repair deficiency. V600E mutation-negative carcinomas were more often sigmoid tumors and usually showed intact mismatch-repair proteins and KRAS or NRAS mutations. The sensitivity and specificity of positive results (strong to moderate staining) of VE1 immunohistochemistry were 85% and 68%, respectively. If any positivity would be considered, then the specificity declined to 51% with no significant improvement of sensitivity. Therefore, only strong positivity should be considered when using the VE1 antibody and Leica Bond-Max automated immunohistochemistry with these parameters. Although VE1 antibody can be useful in the screening of colon carcinomas for BRAF V600E-mutant proteins, molecular genetic confirmation is always necessary for mutation diagnosis.

A further investigation of combined mismatch repair and BRAFV600E mutation specific immunohistochemistry as a predictor of overall survival in colorectal carcinoma

Mutation specific immunohistochemistry (IHC) is a promising new technique to detect the presence of the BRAFV600E mutation in colorectal carcinoma (CRC). When performed in conjunction with mismatch repair (MMR) IHC, BRAFV600E IHC can help to further triage genetic testing for Lynch Syndrome. In a cohort of 1426 patients undergoing surgery from 2004 to 2009 we recently demonstrated that the combination of MMR and BRAFV600E IHC holds promise as a prognostic marker in CRC, particularly because of its ability to identify the poor prognosis MMR proficient (MMRp) BRAFV600E mutant subgroup. We attempted to validate combined MMR and BRAFV600E IHC as a prognostic indicator in a separate cohort comprising consecutive CRC patients undergoing surgery from 1998 to 2003. IHC was performed on a tissue microarray containing tissue from 1109 patients with CRC. The 5 year survivals stratified by staining patterns were: MMRd/BRAFwt 64%, MMRd/BRAFV600E 64%, MMRp/BRAFwt 60% and MMRp/BRAFV600E 53%. Using the poor prognosis MMRp/BRAFV600E phenotype as baseline, univariate Cox regression modelling demonstrated the following hazard ratios for death: MMRd/BRAFwt HR = 0.71 (95%CI = 0.40–1.27), p = 0.31; MMRd/BRAFV600E HR = 0.74 (95%CI = 0.51–1.07), p = 0.11 and MMRp/BRAFwt HR = 0.79 (95%CI = 0.60–1.04), p = 0.09. Although the findings did not reach statistical significance, this study supports the potential role of combined MMR and BRAF IHC as prognostic markers in CRC.

A mutant BRAF V600E-specific immunohistochemical assay: correlation with molecular mutation status and clinical outcome in colorectal cancer

The B-type Raf kinase (BRAF) V600E mutation is a well-established biomarker for poor prognosis in metastatic colorectal cancer (mCRC) and is a highly attractive drug target. A barrier to the development of new therapies targeting BRAF V600E in mCRC is the low prevalence of mutations (approximately 10 %) and the current need for access to sequencing-based technologies which are not routinely available outside of large cancer centres. Availability of a standardised immunohistochemistry (IHC) test, more suited to routine pathology practice, would provide much broader access to patient identification. We sought to evaluate the accuracy and clinical utility of a recently developed BRAF V600E IHC method as a prognostic biomarker in a large cohort of community-based CRC patients. Archival tumour samples from 505 patients with stage I–IV CRC were immunohistochemically tested with two antibodies, pBR1 for total BRAF and VE1 for BRAF V600E. Cases were assessed by two blinded pathologists, and results were compared to BRAF V600E mutation status determined using DNA sequencing. Discordant cases were retested with a BRAF V600E SNaPshot assay. BRAF mutation status was correlated with overall survival (OS) in stage IV CRC. By DNA sequencing and IHC, 505 and 477 patients were respectively evaluable. Out of 477 patients, 56 (11. 7 %) had BRAF V600E mutations detected by sequencing and 63 (13.2 %) by IHC. Using DNA sequencing results as the reference, sensitivity and specificity for IHC were 98.2 % (55/56) and 98.1 % (413/421), respectively. IHC had a positive predictive value (PPV) of 87.3 % (55/63) and a negative predictive value (NPV) of 99.8 % (413/414). Compared to DNA sequencing plus retesting of available discordant cases by SNaPshot assay, IHC using the VE1 antibody had a 100 % sensitivity (59/59), specificity (416/416), NPV (416/416) and PPV (59/59). Stage IV CRC patients with BRAF V600E protein detected by IHC exhibited a significantly shorter overall survival (hazard ratio = 2.20, 95 % CI 1.26–3.83, p = 0.005), consistent with other published series. Immunohistochemistry using the BRAF V600E VE1 antibody is an accurate diagnostic assay in CRC. The test provides a simple, clinically applicable method of testing for the BRAF V600E mutation in routine practice.

BRAFV600E immunohistochemistry in conjunction with mismatch repair status predicts survival in patients with colorectal cancer

Immunohistochemistry has recently been validated for the detection of the BRAFV600E mutation across a range of tumor types. In colorectal carcinoma, the presence of the BRAFV600E mutation can be used to virtually exclude Lynch syndrome in mismatch repair-deficient tumors. In mismatch repair-proficient tumors, BRAFV600E mutation assessed by molecular methods has been proposed as a poor prognostic factor. We investigated whether combined BRAFV600E and mismatch repair status assessment by immunohistochemistry alone can be used as a prognostic marker in the routine clinical setting. We performed immunohistochemistry for BRAFV600E, MLH1, PMS2, MSH2, and MSH6 on 1426 consecutive unselected colorectal carcinomas. Ninety-one (6.4%) carcinomas were mismatch repair-proficient and BRAFV600E mutant, and these tumors demonstrated a significantly worse 5-year survival of 49.7% compared with mismatch repair-proficient BRAF wild type (74.1% of tumors, 65.4% survival), mismatch repair-deficient BRAFV600E mutant (12.9% of tumors, 70.1% survival), and mismatch repair-deficient BRAF wild type (6.6% of tumors, 73.6% survival). The poor survival was confirmed by univariate analysis (P<0.01) but fell away in multivariate analysis (P=0.68) because of the strong effect of tumor stage and age on overall survival. We conclude that in addition to its utility in screening for Lynch syndrome, reflex BRAFV600E and mismatch repair assessment by immunohistochemistry can be used as a powerful predictor of all-cause survival.

Metastatic melanoma mimicking solitary fibrous tumor: report of two cases

Malignant melanomas are known for their remarkable morphological variation and aberrant immunophenotype with loss of lineage-specific markers, especially in recurrences and metastases. Hot spot mutations in BRAF, NRAS, GNAQ, and GNA11 and mutations in KIT are oncogenic events in melanomas. Therefore, genotyping can be a useful ancillary diagnostic tool. We present one case each of recurrent and metastatic melanoma, both showing histological and immunohistochemical features of solitary fibrous tumor (SFT). Mutational analysis detected BRAF and NRAS mutations in the primary and secondary lesions, respectively. This result confirmed the diagnosis of recurrent/metastastic melanoma.

Toward a Molecular Classification of Colorectal Cancer: The Role of BRAF

Different genetic aberrations of BRAF have been reported in various malignancies. BRAF is member of the RAS/RAF/MEK/ERK pathway and constitutive activity of this pathway can lead to increased cellular growth, invasion, and metastasis. The most common activating BRAF mutation in colorectal cancer is the V600E mutation, which is present in 5–15% of all tumors, and up to 80% of tumors with high microsatellite instability (MSI) harbor this mutation. BRAF mutation is associated with proximal location, higher age, female gender, MSI-H, high grade, and mucinous histology, and is a marker of poor prognosis in colorectal cancer. The role of BRAF mutation as a predictive marker in respect of EGFR targeted treatments is controversial. BRAF V600 selective inhibitors have been approved for the treatment of V600 mutation positive metastatic melanoma, but the response rates in colorectal cancer are poor. This might be due to innate resistance mechanisms of colorectal cancers against the treatment solely targeting BRAF. To overcome resistance the combination of treatments, simultaneous inhibition of BRAF and MEK or PI3K/mTOR, might emerge as a successful therapeutic concept.