Stages of Anal Cancer

Cancer stage describes the extent of cancer in the body, such as the size of the tumor, whether it has spread, and how far it has spread from where it first formed. It is important to know the stage of the anal cancer to plan the best treatment. 

There are several staging systems for cancer that describe the extent of the cancer. Anal cancer staging usually uses the TNM staging system. The cancer may be described by this staging system in your pathology report. Based on the TNM results, a stage (I, II, III, or IV, also written as 1, 2, 3, or 4) is assigned to your cancer. When talking to you about your diagnosis, your doctor may describe the cancer as one of these stages. 

Learn about tests to stage anal cancer. Learn more about Cancer Staging.

The following stages are used for anal cancer:

Stage 0 (carcinoma in situ)

In stage 0, abnormal cells are found in the mucosa (innermost layer) of the anus. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called high-grade intraepithelial lesion (HSIL).

Stage I (also called stage 1) anal cancer

In stage I, cancer has formed and the tumor is 2 centimeters or smaller.

Stage II (also called stage 2) anal cancer

Stage II anal cancer is divided into stages IIA and IIB.

• In stage IIA, the tumor is larger than 2 centimeters but not larger than 5 centimeters.
• In stage IIB, the tumor is larger than 5 centimeters.

Stage III (also called stage 3) anal cancer

Stage III anal cancer is divided into stages IIIA, IIIB, and IIIC.

• In stage IIIA, the tumor is 5 centimeters or smaller and has spread to lymph nodes near the anus or groin.
• In stage IIIB, the tumor is any size and has spread to nearby organs, such as the vagina, urethra, or bladder. Cancer has not spread to lymph nodes.
• In stage IIIC, the tumor is any size and may have spread to nearby organs. Cancer has spread to lymph nodes near the anus or groin.

Stage IV (also called stage 4) anal cancer

In stage IV, the tumor is any size. Cancer may have spread to lymph nodes or nearby organs and has spread to other parts of the body, such as the liver or lungs.

Stage IV anal cancer is also called metastatic anal cancer. Metastatic cancer happens when cancer cells travel through the lymphatic system or blood and form tumors in other parts of the body. The metastatic tumor is the same type of cancer as the primary tumor. For example, if anal cancer spreads to the liver, the cancer cells in the liver are actually anal cancer cells. The disease is called metastatic anal cancer, not liver cancer. Learn more in Metastatic Cancer: When Cancer Spreads.

Anal cancer can recur (come back) after it has been treated.

Recurrent anal cancer is cancer that has come back after it has been treated. If anal cancer comes back, it may come back in the anus or in other parts of the body, such as the liver or lungs. Tests will be done to help determine where the cancer has returned. The type of treatment for recurrent anal cancer will depend on where it has come back.

Learn more in Recurrent Cancer: When Cancer Comes Back. Information to help you cope and talk with your health care team can be found in the booklet When Cancer Returns.