Staging and grading of anal cancer

When anal cancer is diagnosed, it is important to know the stage and grade of the cancer. The stage of a cancer describes the size of the tumour and whether it has spread to other parts of the body. The grade of a cancer describes how quickly it is growing.

The most commonly used systems to describe the stage of a cancer are the TNM staging system and the number staging system:

  • TNM staging is more precise and describes the size of the tumour, whether the cancer has spread to the lymph nodes and whether it has spread to other parts of the body.
  • Number staging describes anal cancer in four stages. From stage 1 (small and hasn’t spread to other parts of the body) through to stage 4 (the cancer has spread to other parts of the body).

Knowing the stage and grade of the anal cancer helps with decisions about treatment.

Staging

The stage of a cancer describes its size and if it has spread from where it started. Knowing the stage helps the doctors decide on the best treatment for you.

Generally, anal cancer is divided into four stages. This ranges from cancers that are small and only in the anus (localised) to cancers that have spread to other parts of the body. If the cancer has spread, it is called secondary or metastatic cancer.

If a cancer comes back after it is first treated, it is called a recurrent cancer.

The staging systems most commonly used for anal cancer are:

  • TNM staging
  • the number staging system.


TNM staging system

This system is more complicated. It gives precise information about the tumour stage.


T – Tumour

Doctors put a number next to the T to describe the size and spread of the cancer.

  • Tis – The cancer is at its earliest stage. There are cancerous changes to some of the cells but they are contained (in situ) to only the lining of the anus. If left untreated, these cells may spread into the tissues outside the lining and become an invasive cancer.
  • T1 – The tumour is 2cm or smaller.
  • T2 – The tumour is 2 to 5cm.
  • T3 – The tumour is bigger than 5cm.
  • T4 – The tumour can be any size, but it has started to grow into nearby structures, such as the vagina, bladder or urethra (tube that carries urine from the bladder).

N – Nodes

This describes whether any lymph nodes near the anus contain cancer cells.

  • NX – The lymph nodes were not examined.
  • N0 – There was no cancer in the lymph nodes.
  • N1 – There was cancer in the lymph nodes closest to the rectum (perirectal nodes).
  • N2 – The lymph nodes in the groin (inguinal nodes) or pelvis (pelvic nodes) on one side of the body contained cancer.
  • N3 – This could be either one of the following:
    • There is cancer in the lymph nodes in the rectum and either in the groin or in the pelvis.
    • There is cancer in the lymph nodes in the groin or pelvis, on both sides of the body.

M – Metastasis

Metastasis means that the cancer has spread to other parts of the body.

  • M0 – The cancer has not spread to other parts of the body.
  • M1 – The cancer has spread to other parts of the body, such as the liver or the lymph nodes in the tummy (abdomen).

Our cancer support specialists can tell you more about TNM staging. It’s also important to talk to your doctor for detailed information about your situation.


Number staging

Stage 1

The cancer only affects the anus. It is smaller than 2cm.

Stage 2

The cancer is 2 to 5cm.

Stage 3

This is divided into two stages:

  • Stage 3A – The cancer has spread to the lymph nodes near the rectum or to nearby organs such as the bladder or vagina.
  • Stage 3B – The cancer has spread to lymph nodes in the groin and pelvis, or close to the anus, and to nearby organs such as the bladder or vagina.

Stage 4

The cancer has spread to other parts of the body, such as the liver.


Grading

The grade of a cancer gives doctors an idea of how quickly it may develop. Doctors look at a sample of the cancer cells under a microscope to find the grade.


Grade 1 (low-grade)

The cancer cells look quite similar to normal cells. They usually grow slowly. Doctors sometimes describe them as being well differentiated.

Grade 2 (moderate-grade)

The cancer cells look more abnormal. They are sometimes described as being moderately differentiated.

Grade 3 (high-grade)

The cancer cells look very abnormal and usually grow more quickly. Doctors sometimes describe them as poorly differentiated.

Back to Understanding your diagnosis

Just been diagnosed

Just been diagnosed with cancer? We're here for you every step of the way. There are many ways we can help.

Treatment overview

The main treatment for anal cancer is a combination of radiotherapy and chemotherapy, called chemoradiation.

Cancer registry

Each country in the UK has its own cancer registry: information that helps the NHS and other organisations to plan and improve cancer services.