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 means how big the cancer is and whether it has spread. Your 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 have tests and scans to diagnose your cancer. Further tests find out the stage of your cancer. The staging means how big a cancer is and whether it has 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 TNM system  and the number staging system

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. 

 

TNM stages of anal cancer

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)

The different T stages are

  • TX – the tumour can't be assessed
  • T0 – there is no evidence of a tumour
  • Tis or carcinoma in situ, also called AIN (anal intraepithelial neoplasia) – some of the cells within the lining of the anus have abnormal changes
  • 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 (back passage)
  • N2 – means the lymph nodes in the pelvis (pelvic nodes) or groin (inguinal nodes) on one side of the body contain cancer cells
  • 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 4 main stages in this staging system but doctors sometimes also refer to a stage 0 or AIN.

Stage 0 – 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 of the anus

Your doctor might 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.

Stage 1

This is the earliest stage of an invasive cancer. The tumour is less than 2cm in size and hasn't 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 hasn't 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 might 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: 7 June 2016