Many studies have demonstrated the diagnostic efficiency of DNA hypermethylation of a variety of well-known cancer-related genes, such as p16, RASSF1, APC, MGMT, DAPK, GATA5, and HOX9, in various biofluids, including bronchial aspirates, sputum, serum, plasma, and cell-free circulating DNA [3, 4, 6]. The gene discussed is RASSF1; the disease is cancer.