The stages of anal cancer | Cancer Research UK
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A quick guide to what's on this page

What is staging?

The stage of a cancer tells the doctor how far the cancer has grown or spread. The specialist uses this information to decide on the best treatment for you.

Different staging systems

There are different ways of staging cancers. The 2 main ways are the number staging system and the TNM system. 

There are 5 main number stages

  • Stage 0 means there are abnormal cells within the lining of the anus
  • Stage 1 anal cancer is smaller than 2 cm across
  • Stage 2 anal cancer is larger than 2 cm but has not spread
  • Stage 3 anal cancer has spread into nearby tissues, such as the lymph nodes (glands) or organs that are close by
  • Stage 4 anal cancer has spread to other parts of the body, such as the liver

The TNM system is more detailed. It shows

  • the size of the tumour (T)
  • whether there are cancer cells in the lymph nodes (N)
  • if the cancer has spread to other parts of the body, metastasis (M).

Ask your doctor or nurse specialist to tell you more about the stage of your cancer.

 

CR PDF Icon You can view and print the quick guides for all the pages in the treating anal cancer section.

 

 

What staging is

You will have tests and scans to diagnose your cancer. Further tests will tell doctors about the stage of your cancer. The staging means how far a cancer has grown or spread. Staging helps your doctor to decide on the best treatment for you.

 

Different staging systems

There are different ways of staging cancers. The two main ones are the

The staging of your cancer can be hard to understand. Ask your doctor if it is unclear. If you understand your staging, you will have a better idea of why you are having a particular treatment.

At the end of this section, there is a list of questions for your doctor that may help. 

Read more about the staging of cancer.

 

TNM stages of anal cancer

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

The size of the tumour (T)

The different T stages are

  • TX the tumour can't be assessed
  • T0 no evidence of a tumour
  • Tis or carcinoma in situ, also called AIN (anal intraepithelial neoplasia). This means some of the cells have abnormal changes. The abnormal cells are within the lining of the anus. These cells may develop into invasive cancer if not treated.
  • T1 the tumour measures 2cm or less across
  • T2 the tumour is larger than 2cm but smaller than 5cm
  • T3 the tumour is larger than 5cm
  • T4 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 any lymph nodes (glands) contain cancer cells.  

  • NX nearby lymph nodes can't be assessed
  • N0 no lymph nodes contain cancer cells
  • N1 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 in the groin contain cancer cells OR the nodes on both sides in the pelvis have cancer cells OR the nodes in the groin on both sides of the body and the pelvis contain cancer cells

M stages of anal cancer

The M stage refers to any spread of the cancer (secondary cancers or metastases) to other organs in the body.

  • M0 – cancer cells have not spread to tissues or organs in other parts of the body
  • M1 – cancer cells have spread to tissues and organs in other parts of the body, such as the liver and lungs
 

Number stages of anal cancer

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 within the lining of the anus. The abnormal cells may be inside your back passage (anal canal) or in the skin around the back passage (perianal skin). It is not cancer, but if left untreated, these cells may develop into cancer.

There are different grades of AIN

  • AIN 1 means the abnormal cells are in the lower one third of the skin covering the anus
  • AIN 2 means the abnormal cells are in the lower two thirds of the skin
  • AIN 3 means the abnormal cells are in the full thickness of the skin covering the anus

Your doctor may also refer to AIN as low grade or high grade

  • In low grade AIN (AIN 1 and AIN 2) the cells look almost like normal cells
  • In high grade AIN (AIN 3) the cells look abnormal. AIN 3 is also sometimes called carcinoma in situ.

Low grade AIN may get better without any treatment, and has a low chance of turning into cancer. High grade AIN is less likely to get better without treatment. If left untreated, it may turn into anal cancer. You can read about treatment for AIN in the anal cancer treatment section.

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.

Diagram showing stage 1 anal cance

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.

Diagram showing stage 2 anal cancer

Stage 3

Stage 3 anal cancer has 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.

Diagram showing stage 3 anal cancer

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.

Diagram showing stage 4 anal cancer

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Updated: 11 February 2014