What Is the Cervix?

Common Changes in Cervical Cells
Cell Changes Caused by HPV Are a Special Concern
Other Risk Factors for Cervical Cancer

The cervix is the narrow, lower part of the uterus where it connects to the upper end of the vagina.

The passageway through the cervix is called the endocervical canal. This passageway lets blood flow from the uterus into the vagina during a woman's menstrual period. During childbirth, it opens much wider to let the baby pass through.

The inner lining of the cervix has two different types of cells:

• Tall cells, called glandular cells (or columnar cells) toward the top of the endocervical canal. They make mucus, which helps guard the entrance to the uterus.
• Thin, flat cells, called squamous epithelial cells (or squamous cells). Arranged in layers, they protect the tissues beneath them.

Pap tests can help reveal changes in these cells.

Normal cervical cells	Mix of normal and precancerous cells	Precancerous cervical cells

Common Changes in Cervical Cells

Cervical cells can go through many types of changes that are not cancer. These changes can be caused by:

• Inflammation (redness and swelling)
• An infection (bacterial, viral, or yeast)
• Growths, such as benign (noncancerous) polyps or cysts
• Changes in hormones that occur during pregnancy or menopause

Although many cervical cell changes are very common and not related to cancer, they sometimes make cervical cells look like abnormal cells. So your health care provider may suggest that you repeat your Pap test or have other follow-up tests to be certain that the cell changes are not cancer. (See the tables beginning at Table 1 for more information.)

Cell Changes Caused by HPV Are a Special Concern

Some cervical cell changes are caused by infection with a virus called HPV (human papillomavirus). Most HPV infections eventually go away, or clear, on their own, but sometimes they do not. In infections that do not clear, the HPV-infected cells may become precancerous. If these precancerous cells are not detected and treated early, they can develop into invasive cancer of the cervix. An HPV test can detect the virus in cervical cells.

Other Risk Factors for Cervical Cancer

An ongoing, or persistent, infection with a high-risk HPV type is the most important cause of and risk factor for cervical cancer. However, studies have shown that other factors may act together with HPV to increase a woman's risk of developing cervical cancer. These factors include cigarette smoking, having given birth to many children, and use of birth control pills for five or more years. Also, if you have a weak immune system, you may be at higher risk because your body may not be able to clear HPV infections on its own. For example, if you take medicine to block your body's immune response or if you are infected with HIV, you may be at higher risk of developing cervical cancer.