Normal cervix wall. Light micrograph of a section through healthy tissue from the cervix, as part of a series showing the stages of Cervical Intraepithelial Neoplasia (CIN). CIN is the potentially premalignant transformation and abnormal growth (dysplasia) of squamous cells on the surface of the cervix. CIN is not cancer, and is usually curable. Most cases of CIN remain stable, or are eliminated by the host's immune system without intervention. However a small percentage of cases progress to become cervical cancer, usually cervical squamous cell carcinoma (SCC), if left untreated. The major cause of CIN is chronic infection of the cervix with the sexually transmitted human papillomavirus (HPV). See BQ2724, BQ2725 and BQ2726 for others in the series.