In contrast to CEA (Fig. 1a) and CA15.3 (Fig. 1b), BC patients were associated with high methylation degree of PTEN (77.1 ± 17.9 vs. 24.9 ± 4.5 for benign and 15.1 ± 1.4 for healthy individuals; Fig. 1c) and SMAD4 (70.1 ± 14.4 vs. 28.2 ± 0.61 for benign and 29.5 ± 3.6 for healthy individuals; Fig. 1d). The gene discussed is SMAD4; the disease is breast cancer.