Fig. 1.

NSCLCs hybridized with the ALK break-apart FISH probe (Abbott Molecular). Native ALK status (indicated by yellow arrows) shows fusion of the probes adjacent to the 3′ and 5′ ends of the gene, labeled, respectively, with red and green fluorophores. Rearranged ALK is indicated by the presence of split 3′ (red arrows) and 5′ (green arrows) signals, including single red signals. A, ALK FISH-negative specimen. B, “classic” ALK FISH-positive specimen showing split red and green signals. C, ALK FISH-positive specimen showing two or three copies of single red signals per cell. D, ALK FISH-positive specimen showing evidence of gene copy number increase with clusters of multiple single red and single green signals (double arrows).