Cervical Cancer Prevention and Early Detection

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What is cervical cancer?

Cervical cancer starts in cells lining the cervix. The cervix is the lower part of the uterus (womb). It is sometimes called the uterine cervix. The body of the uterus (the upper part) is where a fetus grows. The cervix connects the body of the uterus to the vagina (birth canal). The part of the cervix closest to the body of the uterus is called the endocervix. The part next to the vagina is the exocervix (or ectocervix). The 2 main types of cells covering the cervix are squamous cells (on the exocervix) and glandular cells (on the endocervix). The place these cell types meet is called the transformation zone. The exact location of the transformation zone changes as you age and with childbirth. Most cervical cancers start in the cells in the transformation zone.

These cells do not suddenly change into cancer. Instead, the normal cells of the cervix gradually develop pre-cancerous changes that turn into cancer. Doctors use several terms to describe these pre-cancerous changes, including cervical intraepithelial neoplasia (CIN), squamous intraepithelial lesion (SIL), and dysplasia. These changes can be detected by the Pap test and treated to prevent cancer from developing (see the sections, “The Pap (Papanicolaou) test” and “Work-up of abnormal Pap test results.”).

Cervical cancers and cervical pre-cancers are classified by how they look under a microscope. There are 2 main types of cervical cancer: squamous cell carcinoma and adenocarcinoma. About 80% to 90% of cervical cancers are squamous cell carcinomas. These cancers form from cells in the exocervix, and the cancer cells have features of squamous cells under the microscope.

Most of the remaining types of cervical cancers are adenocarcinomas. Adenocarcinomas are cancers that develop from gland cells. Cervical adenocarcinoma develops from the mucus-producing gland cells of the endocervix. Cervical adenocarcinomas seem to have become more common in the last 20 to 30 years.

Less commonly, cervical cancers have features of both squamous cell carcinomas and adenocarcinomas. These are called adenosquamous carcinomas or mixed carcinomas.

Although cervical cancers start from cells with pre-cancerous changes (pre-cancers), only some women with pre-cancers of the cervix will develop cancer. The change from pre-cancer to cancer usually takes several years − but it can happen in less than a year. For most women, pre-cancerous cells will remain unchanged or even go away without any treatment. Still, in some women pre-cancers turn into true (invasive) cancers. Treating all pre-cancers can prevent almost all true cancers. Pre-cancerous changes are discussed in the section “Work-up of abnormal Pap test results” and treatment of pre-cancers is discussed in the section, “How women with abnormal Pap test results or pre-cancers are treated.”

Last Medical Review: 09/17/2014
Last Revised: 07/19/2016