Deftereos G, et al. - Experts sought to investigate if DNA extracted from TTF-1 IHC slides, a common stain for lung adenocarcinoma, can be tested for EGFR mutations. In this study, 22 lung adenocarcinoma samples (11 EGFR wild-type and 11 mutated) were selected. For TTF-1 IHC, slides were stained. They performed pyrosequencing for mutations in exons 18, 19, 20 and 21 of EGFR and compared the results with clinical EGFR testing data. They found identical results of all 11 originally EGFR wild-type cases on the TTF-1 samples. For molecular testing, TTF-1 IHC slides can be a viable DNA source, particularly important in lung biopsies with insufficient material following diagnostic evaluation.