Several genes exhibit frequent methylation in NSCLC and other tumor types, such as the tumor suppressor gene adenomatosis polyposis coli (APC) or retinoic acid receptor beta (RARβ), but these genes are often also methylated in counterpart benign tissue, especially in tumors for which field effects are common, such as NSCLC [18,61]. The gene discussed is RARB; the disease is non-small cell lung carcinoma.