Cervical intraepithelial neoplasia (CIN), also known as cervical dysplasia, is the abnormal growth of cells on the surface of the cervix that could potentially lead to cervical cancer. More specifically, CIN refers to the potentially precancerous transformation of cells of the cervix. CIN most commonly occurs at the squamocolumnar junction of the cervix, a transitional area between the squamous epithelium of the vagina and the columnar epithelium of the endocervix. It can also occur in vaginal walls and vulvar epithelium. CIN is graded on a 1–3 scale, with 3 being the most abnormal (see classification section below). Human papillomavirus (HPV) infection is necessary for the development of CIN, but not all with this infection develop cervical cancer. Many women with HPV infection never develop CIN or cervical cancer. Typically, HPV resolves on its own. However, those with an HPV infection that lasts more than one or two years have a higher risk of developing a higher grade of CIN.Like other intraepithelial neoplasias, CIN is not cancer and is usually curable. Most cases of CIN either remain stable or are eliminated by the persons immune system without need for intervention. However, a small percentage of cases progress to cervical cancer, typically cervical squamous cell carcinoma (SCC), if left untreated. Signs and symptoms
There are no specific symptoms of CIN alone.
The grade of squamous intraepithelial lesion can vary. CIN is classified in grades:

Changes in Terminology
The College of American Pathology and the American Society of Colposcopy and Cervical Pathology came together in 2012 to publish changes in terminology to describe HPV-associated squamous lesions of the anogenital tract as LSIL or HSIL as follows below:CIN 1 is referred to as LSIL. CIN 2 that is negative for p16, a marker for high-risk HPV, is referred to as LSIL. Those that are p16-positive are referred to as HSIL. CIN 3 is referred to as HSIL. Screening
The two screening methods available are the Pap smear and testing for HPV.CIN is usually discovered by a screening test, the Pap smear. The purpose of this test is to detect potentially precancerous changes through random sampling of the transformation zone. Pap smear results may be reported using the Bethesda system (see above). The sensitivity and specificity of this test were variable in a systematic review looking at accuracy of the test. An abnormal Pap smear result may lead to a recommendation for colposcopy of the cervix, an in office procedure during which the cervix is examined under magnification. A biopsy is taken of any abnormal appearing areas.Colposcopy can be painful and so researchers have tried to find which pain relief is best for women with CIN to use.