Usefulness of cytological samples (CS) for the assessment of ALK rearrangements in non-small cell lung cancer (NSCLC).

e18008 Background: ALK gene rearrangements define a new molecular subtype of NSCLC with response to Crizotinib, a dual MET and ALK inhibitor. Analysis of ALK rearrangements has been performed in biopsies or surgical specimens. However, advanced NSCLC is often diagnosed by FNA cytology obtained through minimally invasive techniques, and frequently CS are the only tumour sample available. We assessed the feasibility of determining ALK rearrangements in CS. Methods: We studied prospectively ALK rearrangements in 53 CS from 53 NSCLC patients (30 M/23 F) by FISH (Vysis dual colour break apart probe). We considered positive for ALK rearrangement when > 15% of cells show splits signals. Tumor samples were obtained by bronchoscopy -FNA in 26 cases (49.1%), EBUS-FNA in 7 (13.2%), EUS-FNA in 3 cases (5.7%), CT-FNA in 3 (5.7%), and direct FNA in 6 cases (11.3%). Two cavity fluids (3.8%), 4 imprints (7.5%), and 2 cellblocks received for consultation (3.8%) were also studied. FISH was performed on non-stained ThinPrep...