The cervix is the lower third portion of the uterus (womb). It serves as a neck to connect the uterus to the vagina. The opening of the cervix, called the os, remains small and narrow, except during childbirth when it widens to allow a baby to pass from the uterus into the vagina.
The uterus is a hollow muscular organ located in the female pelvis between the bladder and rectum. The ovaries produce the eggs that travel through the fallopian tubes. Once the egg has left the ovary it can be fertilized and implant itself in the lining of the uterus. The main function of the uterus is to nourish the developing fetus prior to birth.
Cervical cancer develops in the thin layer of cells called the epithelium, which cover the cervix. Cells found in this tissue have different shapes:
- Squamous cells (flat and scaly). Most cervical cancer arises from changes in the squamous cells of the epithelium (squamous cell carcinoma).
- Columnar cells (column-like). These cells line the cervical glands. Cancers found here are known as adenocarcinomas.
- Mixed carcinomas are cells that combine features of squamous cells and adenocarcinomas.
Cervical cancer usually begins slowly with precancerous abnormalities, and even if cancer develops, it generally progresses very gradually. Cervical cancer is the most preventable type of cancer and is very treatable in its early stages. Regular Pap tests and human papillomavirus (HPV) screening can help detect this disease early.
Precancerous Changes in the Cervix
Dysplasia is a term that refers to a precancerous condition. It may become cancerous, but not always. In the case of cervical cancer, dysplasia indicates that the layer of cells that covers the cervix (squamous epithelial cells) are abnormal in size and shape and are beginning to grow. However, the cells are still confined to the surface (epithelial layer)
These types of changes are generally first noted in the results of a Pap smear. They will be reported as one of the following:
- Atypical squamous cells (ASC)
- Low-grade squamous intraepithelia lesion (LGSIL)
- High-grade squamous intraepithelial lesion (HGSIL)
(See Pap smear section in Diagnosis for more detail about these terms.)
If further testing is needed, a colposcopy is usually performed. Results for colposcopy are reported as cervical intraepithelial neoplasia (CIN).These precancerous changes are categorized according to severity: CIN I, CIN II, and CIN III. (See Colposcopy section in Diagnosis for more detail about these terms.)
CIN III is considered the same as carcinoma in situ (CIS) or Stage 0 cervical cancer. The cancer has not yet invaded deeper tissues. However, if not surgically removed, there is a high chance it can progress to invasive cancer.Click the icon to see an image of cervical dysplasia.
Invasive Cervical Cancer
The cells of the epithelium rest on a very thin layer called the basement membrane. Invasive cervical cancer occurs when cancer cells in the epithelium cross this membrane and invade the stroma, the underlying supportive tissue of the cervix.
In later stages, the original cancer may spread to areas surrounding the uterus and cervix or near organs such as the bladder or rectum. It may also spread to distant sites in the body through the bloodstream or the lymph nodes.