RT Journal Article SR Electronic T1 Diamond: immunohistochemistry versus sequencing in EGFR analysis of lung adenocarcinomas JF Journal of Clinical Pathology JO J Clin Pathol FD BMJ Publishing Group Ltd and Association of Clinical Pathologists SP 440 OP 447 DO 10.1136/jclinpath-2015-203348 VO 69 IS 5 A1 Ragazzi, Moira A1 Tamagnini, Ione A1 Bisagni, Alessandra A1 Cavazza, Alberto A1 Pagano, Maria A1 Baldi, Licia A1 Boni, Corrado A1 Cantile, Flavia A1 Barbieri, Fausto A1 Nicoli, Davide A1 Sartori, Giuliana A1 de Biase, Dario A1 Gardini, Giorgio A1 Rossi, Giulio YR 2016 UL http://jcp.bmj.com/content/69/5/440.abstract AB Aims Identification of epidermal growth factor receptor (EGFR) mutations in lung adenocarcinomas is the single most important predictor of clinical response and outcome using EGFR tyrosine kinase inhibitors (TKIs). EGFR E746-A750del and L858R mutations are the most common gene alterations, also predicting the best clinical response to TKIs. We evaluated the accuracy of EGFR mutation-specific antibodies in a large cohort of lung adenocarcinomas, with different molecular settings and types of tissue samples.Methods 300 lung adenocarcinomas diagnosed on cytology (48 cell blocks), biopsy (157 cases) and surgical resections (95 cases) were selected. All cases were investigated for EGFR by sequencing and two mutation-specific antibodies (clone 6B6 for E746-A750del; clone 43B2 for L858R) were tested using an automated immunostainer. Discordant results were investigated by next-generation sequencing (NGS).Results Overall sensitivity and specificity of mutant-specific antibodies were 58.6% and 98.0%, respectively, and they increased up to 84% and 100% if only tumours harbouring E746-A750del were considered. In 13 discordant cases, NGS confirmed immunohistochemistry results in eight samples.Conclusions The EGFR mutation-specific antibodies have a fair/good sensitivity and good/high specificity in identifying classic mutations, but they cannot replace molecular tests. The antibodies work equally well on biopsies and cell blocks, possibly permitting a rapid screening in cases with poor material.