Researchers have recently suggested the use of aberrant CpG island methylation for early detection of lung cancer, and tumor‐suppressor genes are considered a molecular marker system in the promoter region for early identification of lung cancer, for example, cyclin‐dependent kinase inhibitor 2A (p16INK4A), O6‐methylguanine‐DNA methyltransferase (MGMT), and retinoic acid receptor beta (RARB).76 Here, RARB is linked to lung carcinoma.