CIN is a short form for “Cervical Intraepithelial Neoplasia”. It is a condition in which the healthy cells in the cervix (neck of the womb) undergo abnormal changes. The cervix is a cylindrical organ situated at the lowest part of the uterus. It has an outer surface which is covered by squamous cells and an inner surface lined by another type of cells called columnar cells. The area where these two types of cells meet is called the squamo-columnar junction. It is usually around this area that abnormal changes in the squamous cells take place. These cells do not invade into the deeper layers of the cervix or spread to other organs through blood or lymphatic vessels. But if left untreated, they have the potential to turn into cancer.
CIN is caused by human papillomavirus (HPV). Of the over 100 types of HPV viruses, only about 20 are responsible for the abnormal changes in the cells. About 4 out of 5 adult women would have had cervical HPV infection at some time in their lives, and only a small number develop precancerous changes and a few finally progress to cervical cancer.
Most patients with CIN have no symptoms. Occasionally, abnormal vaginal bleeding may occur. The cell changes are not visible to the naked eye and can only be suspected by an abnormal Pap smear or HPV DNA test. Diagnosis is made by biopsy of the cervix using a magnifying telescope (colposcope).
CIN represents a spectrum of disease, ranging from CIN I (about one third of the cervical cells are abnormal ) to CIN2 (almost two third of the cells are abnormal) and CIN3 (almost all the cervical cells are abnormal).
It is estimated that one out of six women will develop CIN 1, which usually resolves itself as the virus is cleared by the women’s own immune system. Further treatment is not required.
But women with CIN 2 and CIN 3 may not spontaneously clear the lesion. They need further follow-up examinations and treatment to destroy the abnormal cells .The energy sources used include heat (electro cautery), laser and freezing techniques (cryotherapy).
Although treatment of CIN 2 and CIN 3 using above modalities is generally effective, follow-up exams are essential. Consensus guidelines published in 2006 by the American Journal of Obstetrics & Gynecology (AJOG) report that the failure rate for the treatment processes is generally 5-15 percent. As a result, the incidence of invasive cervical cancer among women previously treated for CIN 2 and CIN 3 is substantially greater than in the general U.S. female population.
For women who have completed the family or who do not wish to have any more children , removal of the womb (hysterectomy)may be another option. If treated early, CIN is 100% curable.
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