Methylation proportions at 18 CpG sites within the HPV 16 genome in DNA samples from various cervical lesions, and the mean methylation proportion of all DNA samples at each CpG site. CpG, cytosine-phosphate-guanine; HPV, human papilloma virus; LSIL, low-grade intraepithelial lesions; HSIL, high-grade intraepithelial lesions; CC, cervical cancer.