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Original Article


Clinical utility of immunohistochemistry using the novel anti-BRAF V600E antibody (clone RM8) for detection of the BRAF V600E mutant protein in papillary thyroid cancers

Arvind KrishnamurthyVijayalakshmi RamshankarKanchan MurhekarVidyarani ShyamsundarPavithra B. DesaiPurvish Parikh
Department of Surgical Oncology, Cancer Institute (WIA), Adyar, Chennai, India1Department Preventive Oncology Research, Cancer Institute (WIA), Adyar, Chennai, India, 2Department of Pathology, Cancer Institute (WIA), Adyar, Chennai, India, 3Department Oral Pathology, Balaji Dental College, Chennai, India, 4Director of Precision Oncology, Asian Cancer Institute, Mumbai, Maharastra, India, 
Corresponding Author:

Arvind Krishnamurthy

Department of Surgical Oncology, Cancer Institute (WIA), 38, Sardar Patel Rd, Adyar, Chennai- 600036
E-mail: drarvindkrishnamurthy@yahoo.co.in

Corresponding Author:

Arvind Krishnamurthy

Department of Surgical Oncology, Cancer Institute (WIA), 38, Sardar Patel Rd, Adyar, Chennai- 600036
E-mail: drarvindkrishnamurthy@yahoo.co.in

DOI:10.18203/issn.2456-3994.IntJMolImmunoOncol20180471

ABSTRACT


Background: Molecular markers are gaining increasing importance as diagnostic and prognostic tools in patients with well differentiated thyroid cancers and BRAF V600E mutation has received wide attention in this regard Aim: To evaluate the clinical value of immunohistochemistry (IHC) using anti-BRAF V600E antibody (clone RM8) for detection of the BRAF V600E mutant protein in formalin-fixed and paraffin-embedded tissues of patients with papillary thyroid carcinomas. Materials and Methods: Patients who were managed for well differentiated thyroid cancers (n = 79) during the years 2005 and 2006 were included in the study. We evaluated the fidelity of the RM8 antibody specific for the BRAF V600E and compared its detection accuracy to real time polymerase chain reaction (PCR), which was taken as the gold standard. Results: Mutant BRAF V600E antibody was studied in 79 tissue sections, out of which 21 (26.5%) had staining for BRAF V600E in >20% of the tumour cells and these were considered positive. The BRAF staining was moderate in 10 (47.6%), strong in 9 (42.5%) and very strong in 2 (9.5%) of sections stained. There was a statistically significant concordance (P = 0.000) with quantitative PCR (qPCR) for BRAF mutant taken as standard. (Kappa agreement: 0.881) Further, the receiver operating characteristics (ROC) curve showed that IHC can be used as a comparable standard to the qPCR. The highest possible sensitivity of 92% and specificity of 92.6% could be achieved by considering the cytoplasmic positivity of >20% of cells with moderate to strong intensity (AUC = 0.923) Conclusion: Our study has shown that BRAF V600E IHC can be done in a conventional manner using rabbit monoclonal antibody RM8 on formalin-fixed and paraffin-embedded tissues of patients with papillary thyroid carcinomas. With a comparable diagnostic accuracy to the gold standard qPCR testing and with an added advantage of being cost effective, this technology can be considered for use as a first-line method for detection of BRAF V600E mutations, especially in resource constrained settings.
Keywords: Anti-BRAF V600E antibody, BRAF V600E mutant protein, Clone RM8, Immunohistochemistry, Papillary thyroid cancers, Polymerase chain reaction

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