CDO1 and ovarian cancer: While methylation levels of two markers were significantly increased in clinician-taken cervical scrapes of ovarian cancer patients as compared to healthy controls (C2CD4D, P = 0.001; CDO1, P = 0.004, Mann–Whitney U), benign and malignant ovarian masses could not be distinguished using these markers (Fig. 2 and Supplemental Fig. 5).