Utilization of a MAB for BRAFV600E detection in papillary thyroid carcinoma

M Bullock; C O'Neill; A Chou; A Clarkson; T Dodds; C Toon; M Sywak; S B Sidhu; L W Delbridge; B G Robinson; D L Learoyd; D Capper; A von Deimling; R J Clifton-Bligh; A J Gill

doi:10.1530/ERC-12-0239

Utilization of a MAB for BRAF^V600E detection in papillary thyroid carcinoma

¹Hormones and Cancer Group, Cancer Genetics Laboratory, Kolling Institute of Medical Research and
²Department of Endocrine Surgery, Royal North Shore Hospital, Sydney, New South Wales 2065, Australia
³Department of Anatomical Pathology, SYDPATH, St Vincents Hosptial, Darlinghurst, New South Wales 2010, Australia Departments of
⁴Anatomical Pathology and
⁵Endocrinology, Royal North Shore Hospital, Sydney, New South Wales 2065, Australia
⁶Department of Neuropathology, Institute of Pathology, Ruprecht‐Karls University, Heidelberg, Germany
⁷Clinical Cooperation Unit Neuropathology, DKFZ, Heidelberg, Germany
⁸Northern Cancer Translational Research Unit, Royal North Shore Hospital, Sydney, New South Wales 2065, Australia
⁹University of Sydney, Sydney, New South Wales 2006, Australia

(Correspondence should be addressed to Anthony J Gill at Department of Anatomical Pathology, Royal North Shore Hospital; Email: affgill{at}med.usyd.edu.au)

Abstract

Identification of BRAF^V600E in thyroid neoplasia may be useful because it is specific for malignancy, connotes a worse prognosis, and is the target of novel therapies currently under investigation. Sanger sequencing is the ‘gold standard’ for mutation detection but is subject to sampling error and requires resources beyond many diagnostic pathology laboratories. In this study, we compared immunohistochemistry (IHC) using a BRAF^V600E mutation-specific MAB to Sanger sequencing on DNA from formalin-fixed paraffin-embedded tissue, in a well-characterized cohort of 101 papillary thyroid carcinoma (PTC) patients. For all cases, an IHC result was available; however, five cases failed Sanger sequencing. Of the 96 cases with molecular data, 68 (71%) were BRAF^V600E positive by IHC and 59 (61%) were BRAF^V600E positive by sequencing. Eleven cases were discordant. One case was negative by IHC and initially positive by sequencing. Repeat sequencing of that sample and sequencing of a macrodissected sample were negative for BRAF^V600E. Of ten cases positive by IHC but negative by sequencing on whole sections, repeat sequencing on macrodissected tissue confirmed the IHC result in seven cases (suggesting that these were false negatives of sequencing on whole sections). In three cases, repeat sequencing on recut tissue remained negative (including using massive parallel sequencing), but these cases demonstrated relatively low neoplastic cellularity. We conclude that IHC for BRAF^V600E is more sensitive and specific than Sanger sequencing in the routine diagnostic setting and may represent the new gold standard for detection of BRAF^V600E mutation in PTC.