The stages of anal cancer

The stage of a cancer tells the doctor how far the cancer has grown or spread. This is important, as your specialist will use this information to decide on the most suitable treatment for you. The tests and scans you have when diagnosing your cancer give some information about the stage.

There are different ways of staging cancers. The two main ways are the TNM system and the number staging system.

The information you get about the stage of your cancer may sound a bit confusing. You probably won't be as familiar with these terms as your doctor is. If you don't understand what stage your cancer is, and would like to know more, do ask your doctor or nurse specialist.

Knowing the stage of your cancer may help you understand why your doctors have chosen a particular treatment for you. At the end of this section, there is a list of questions for your doctor that may help. There is more about staging cancers in the about cancer section.

TNM stands for Tumour, Node, and Metastasis. This staging system can tell you

• The size of a primary tumour (T)
• Whether there are lymph nodes containing cancer cells (N)
• Whether the cancer has spread to a different part of the body (M)

The size of the tumour (T)

There are 5 stages of tumour size in the current TNM classification of anal cancer. It goes from T1 to T4 and there is a very early, pre cancerous stage called Tis or carcinoma in situ. 

• Tis or carcinoma in situ is also called AIN (anal intraepithelial neoplasia). This means some of the cells have cancerous changes. But these abnormal cells are contained within the lining of the anus. If left untreated these cells may develop into invasive cancer.
• T1 means the tumour measures 2cm across or less
• T2 means the tumour is larger than 2cm but smaller than 5cm
• T3 means the tumour is larger than 5cm
• T4 means the cancer can be any size, but is growing into the surrounding tissues or organs, such as the urethra, the vagina or bladder

N stages of anal cancer

The N stage refers to whether the cancer cells have spread into any lymph nodes. The N stages are defined as follows

• N0 means that no lymph nodes contain cancer cells
• N1 means there are cancer cells in the lymph nodes closest to the rectum
• N2 means the lymph nodes in the pelvis (pelvic nodes) or groin (inguinal nodes) on one side of the body are affected
• N3 means that either the nodes near the rectum and nodes in the groin or pelvis contain cancer cells OR the nodes in the pelvis or groin on both sides of the body contain cancer cells

M stages of anal cancer

The M stage refers to whether the cancer cells have spread to other organs in the body. M stages are defined as follows

• M0 means there is no cancer spread to other organs
• M1 means the cancer has spread to another part of the body, such as the liver.

There are four main stages in this staging system, but doctors sometimes also refer to a stage 0 or AIN.

Stage 0 or anal carcinoma in situ (AIN)

This is when abnormal cells are contained within the lining of the anus. If left untreated, these cells may develop into cancer. 

Stage 1

This is the earliest stage of an invasive cancer. The tumour is less than 2cm in size and has not spread to any of the nearby tissues, lymph nodes or other organs. Stage 1 is the same as T1, N0 and M0 in the TNM stages.

Stage 2

The cancer is larger than 2cm but has not spread anywhere else in the body. Stage 2 is the same as T2-3, N0, M0 in the TNM staging system.

Stage 3

Stage 3 anal cancer is divided into 2 sub groups:

Stage 3A - the cancer is of any size and may have spread into nearby lymph nodes or organs. Stage 3 is the same as T1-3, N1, M0, or T4, N0, M0.

Stage 3B - the cancer is of any size and has spread to the lymph nodes in the groin or the pelvis, and may also have grown into nearby organs. Stage 3B is the same as T4, N1, M0 or Any T, N2-3, M0.

Stage 4

The cancer is of any size and has spread to other parts of the body such as the liver. Stage 4 is the same as any T, any N and M1.