Cervical intraepithelial neoplasia, or CIN, is the abnormal growth of potentially precancerous cells in the cervix. Most cases of CIN remain stable, or are eliminate by the host's immune system without intervention. However a small percentage of cases progress to become cervical cancer, usually cervical squamous cell carcinoma, or SCC. The major cause of CIN is infection with the sexually transmitted human papillomavirus (HPV), usually the high-risk HPV types 16 or 18.