PTCH1 and cervical squamous intraepithelial neoplasia: Low frequency (14–16%) of PTCH1 methylation was seen in the asymptomatic exfoliated cervical cells and in the normal epithelium adjacent to the tumor, followed by a significant increase in CIN (31%) in stage I/II (57%) and comparable CIN in stage III/IV (58%) 97.The methylation frequency is also different in pathological classification.