Cervical intraepithelial neoplasia (CIN) is an abnormality of the cervical epithelium associated with HPV infection and is considered a precancerous lesion of the cervix.CIN is classified into three levels: 1, 2 and 3.CIN I represents mild atypical hyperplasia involving only the subepithelial third of the cervix; 70-90% of CIN I lesions resolve spontaneously.CIN II and III represent moderate to severe atypical hyperplasia involving the subepithelial third of the cervix to the whole layer, respectively. CIN II and III represent moderate to severe atypical hyperplasia involving the subepithelial 2/3 to the whole layer, respectively. More than half of CIN II and III persist or eventually progress to squamous carcinoma. Persistent HPV infection can also lead to adenocarcinoma in situ of the cervix. In the United States, the use of Pap test screening to diagnose these precancerous lesions has reduced the incidence of cervical cancer. These precancerous lesions can occur within 5 years of HPV infection.