This condition may progress if untreated but is often self-limiting, returning to normal without treatment. At this stage, cells are malignant but still confined to the original site. It may take one or two years for CIS to progress to invasive cancer, but because cancer is unpredictable, this condition should be treated as soon as possible. The cells of the epithelium rest on a very thin layer called the basement membrane, which separates them from the underlying supportive tissue, or stroma, of the cervix. Invasive cervical cancer occurs in the epithelium when cancer cells penetrate the basement membrane and invade the stroma.
Cervical cancer is the second most common cancer of the female reproductive system.
Because of the Pap smear, the rates of invasive cervical cancer have been declining for years. Of some concern, however, are reports that although squamous cell cervical cancer is declining, cervical adenocarcinoma, which occurs in the glands associated with the cervix, may be on the increase. About 13,700 American women will be diagnosed with invasive cervical cancer and 65,000 with precancerous lesions this year. A woman who has never been sexually active has a very low risk for developing cervical cancer. Researchers believe that most cervical cancers develop when viruses damage certain protective genes, particularly one known as tumor suppressor gene p53.