Published studies using reverse transcriptase-polymerase chain reaction (RT-PCR) analysis or fluorescent in situ hybridization (FISH) to characterize EML4-ALK fusions in lung cancer have revealed frequencies ranging from 0.5% to 7.5% in general lung cancer patients and a frequency of 13.5% in clinical factor-enriched cases [23], [27,28]. This evidence concerns the gene ALK and lung cancer.