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Cervical cancer starts in the cells lining the cervix -- the lower part of the uterus (womb). The cervix connects the body of the uterus (the upper part where a fetus grows) to the vagina (birth canal). Cancer starts when cells in the body begin to grow out of control. To learn more about how cancers start ands spread, see What Is Cancer?
The cervix is made of two parts and is covered with two different types of cells.

• The endocervix is the opening of the cervix that leads into the uterus. It is covered with glandularcells.
• The exocervix (or vrctocervix) is the outer part of the cervix that can be seen by the doctor during a speculum exam. It is covered in squamous cells.

The place where these two cell types meet in the cervix is called the transformation zone. The exact location of the transformation zone changes as you get older and if you give birth. Most cervical cancers begin in the cells in the transformation zone.

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Cervical cancers and cervical pre-cancers are classified by how they look in the lab with a microscope. The main types of cervical cancers are squamous cell carcinoma and adenocarcinoma.

• Most (up to 9 out of 10) cervical cancers are squamous cell carcinomas. These cancers develop from cells in the exocervix. Squamous cell carcinomas most often begin in the transformation zone (where the exocervix joins the endocervix).
• Most of the other cervical cancers are adenocarcinomas. Adenocarcinomas are cancers that develop from glandular cells. Cervical adenocarcinoma develops from the mucus-producing gland cells of the endocervix.
• Less commonly, cervical cancers have features of both squamous cell carcinomas and adenocarcinomas. These are called adenosquamous carcinomas or mixed carcinomas.

Although almost all cervical cancers are either squamous cell carcinomas or adenocarcinomas, other types of cancer also can develop in the cervix. These other types, such as melanoma, sarcoma, and lymphoma, occur more commonly in other parts of the body.

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