Anal cancer

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Stages of anal cancer

Staging describes or classifies a cancer based on how much cancer there is in the body and where it is when first diagnosed. This is often called the extent of cancer. Information from tests is used to find out the size of the tumour, which parts of the organ have cancer, whether the cancer has spread from where it first started and where the cancer has spread. Your healthcare team uses the stage to plan treatment and estimate the outcome (your prognosis).

The staging system for anal cancer applies only to carcinomas. For carcinomas of the perianal skin, only tumours within 5 cm from the anus are staged with the following system.

The most common staging system for anal cancer is the TNM system. For anal cancer there are 5 stages – stage 0 followed by stages 1 to 4. Often the stages 1 to 4 are written as the Roman numerals I, II, III and IV. Generally, the higher the stage number, the more the cancer has spread. Talk to your doctor if you have questions about staging.

When describing the stage, doctors may use the words local, regional or distant. Local means that the cancer is only in area around the anus (anal canal or perianal skin) and has not spread to other parts of the body. Regional means close to the anus or around it. Distant means in a part of the body farther from the anus.

Find out more about staging cancer.

Stage 0 (carcinoma in situ)

The tumour or abnormal cells are only in the top layer of anal tissue. Stage 0 includes high-grade anal intraepithelial neoplasia (AIN) and Bowen’s disease of the anus.

Stage 1

The tumour is 2 cm or smaller.

Stage 2A

The tumour is larger than 2 cm but not more than 5 cm.

Stage 2B

The tumour is larger than 5 cm.

Stage 3A

The tumour is 5 cm or smaller. The cancer has also spread to nearby lymph nodes, including lymph nodes in the groin, around the rectum or in the pelvis.

Stage 3B

The tumour has grown into nearby organs such as the bladder, urethra or vagina.

Stage 3C

The tumour is larger than 5 cm or has grown into nearby organs, such as the bladder, urethra or vagina. The cancer has also spread to nearby lymph nodes, including lymph nodes in the groin, around the rectum or in the pelvis.

Stage 4

The cancer has spread to other parts of the body (called distant metastasis), such as to the liver, lungs, or bone. This is also called metastatic anal cancer.

Recurrent anal cancer

Recurrent anal cancer means that the cancer has come back after it has been treated. If it comes back in the same place that the cancer first started, it’s called local recurrence. If it comes back in tissues or lymph nodes close to where it first started, it’s called regional recurrence. It can also recur in another part of the body. This is called distant metastasis or distant recurrence.

Bowen's disease

A condition that affects the skin. Signs include red, crusty sores or scaly patches on the skin that grow slowly and do not heal. It is an early stage of skin cancer (carcinoma in situ).

Bowen’s disease is usually caused by exposure to arsenic or the sun.


The muscular sac in the pelvis that receives urine from the ureters (tubes that carry urine from the kidneys), stores it and passes it from the body through the urethra.


The tube that carries urine from the bladder to the outside of the body.

In males, the urethra passes through the prostate and penis and carries semen as well as urine. In females, the urethra opens above the vaginal opening.


The muscular tube found in the pelvis of women between the bladder and rectum. The vagina extends from the cervix (the lower part of the womb) to the vulva (the outer part of the genitals).

Menstrual fluid passes out of the body through the vagina. During childbirth, the baby passes through the vagina.

Also called the birth canal.


Dr Shawn Li I’m extremely grateful to the Canadian Cancer Society for funding my research with an Innovation Grant.

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Cancer affects all Canadians

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