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.
Generally, signs and symptoms of cervical cancer include:
abnormal or post-menopausal bleeding
abnormal discharge
changes in bladder or bowel function
pelvic pain on examination
abnormal appearance or palpation of cervix.HPV infection of the vulva and vagina can cause genital warts or be asymptomatic. Causes
The cause of CIN is chronic infection of the cervix with HPV, especially infection with high-risk HPV types 16 or 18. It is thought that the high-risk HPV infections have the ability to inactivate tumor suppressor genes such as the p53 gene and the RB gene, thus allowing the infected cells to grow unchecked and accumulate successive mutations, eventually leading to cancer.Some groups of women have been found to be at a higher risk of developing CIN:
Infection with a high-risk type of HPV, such as 16, 18, 31, or 33
Immunodeficiency (e.g. HIV infection)
Poor diet
Multiple sex partners
Lack of condom use
Cigarette smokingAdditionally, a number of risk factors have been shown to increase an individuals likelihood of developing CIN 3/carcinoma in situ (see below):
Women who give birth before age 17
Women who have > 1 full term pregnancies

Pathophysiology
The earliest microscopic change corresponding to CIN is epithelial dysplasia, or surface lining, of the cervix, which is essentially undetectable by the woman. The majority of these changes occur at the squamocolumnar junction, or transformation zone, an area of unstable cervical epithelium that is prone to abnormal changes. Cellular changes associated with HPV infection, such as koilocytes, are also commonly seen in CIN.