Diamond project: Immunohistochemical screening using EGFR mutation-specific antibodies in lung adenocarcinomas

e19035 Background: Identification in lung adenocarcinomas (LACs) of epidermal growth factor receptor (EGFR) mutations is the single most important predictor of clinical response and outcome using EGFR tyrosine kinase inhibitors (TKI). We evaluated the accuracy of EGFR mutation-specific antibodies in LACs and showing different molecular settings and detected on cytology and histologic samples. Methods: 111 LACs diagnosed on cytology (21 cell blocks), biopsy (58 cases) and surgical resections (32 cases) were selected for the study. All cases were previously investigated by Sanger sequencing and/or pyrosequencing (EGFR exons 18 to 21; KRAS exon 2) and ALK status by Immunohistochemistry (IHC)/FISH. IHC using EGFR mutation-specific antibodies (clone 6B6 for delE746-A750 and clone 43B2 for L858R; Cell Signalling Technologies, Danvers, MA) were tested using an automated immunostainer (Benchmark, Ventana Inc, Tucson, AZ). Cases were quoted as positive when at least 2+ staining was present in at least 5% of tumor ...