In NSCLC, CHFR promoter CpG island methylation occurs in approximately 10–40 % of NSCLCs characterized by wild-type EGFR and KRAS in absence of ALK gene rearrangement, which implicates that CHFR promoter CpG island methylation occurs in a specific NSCLC subgroup [47]. Here, ALK is linked to non-small cell lung carcinoma.