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 number staging system and the TNM staging system:

  • 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).
  • TNM staging is more precise and looks at 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.

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

Staging

The stage of a cancer describes its size and whether it has spread from where it started. Knowing the extent of the cancer helps the doctors to decide on the most appropriate treatment.

Generally, anal cancer is divided into four stages, ranging from small and localised, to cancer that has spread to other parts of the body. If the cancer has spread, this is known as secondary or metastatic cancer.

If the cancer comes back after initial treatment, it’s known as recurrent cancer.

The most commonly used staging systems are number staging and the TNM staging system.


Number staging

Stage 1

The cancer only affects the anus and is smaller than 2cm in size. It has not begun to spread into nearby lymph nodes or to the sphincter muscle.

Stage 2

The cancer is bigger than 2cm in size, but hasn’t spread into nearby lymph nodes or to other parts of the body.

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 to lymph nodes close to the anus, as well as nearby organs such as the bladder or vagina.

Stage 4

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


TNM staging system

This system is more complex and can give more precise information about the tumour stage than the number staging system.

T – Tumour

Doctors put a number next to the ‘T’ to describe the size and spread of the cancer.

Tis – This means the cancer is at its earliest stage (in situ).

There are cancerous changes to some of the cells, but the abnormal cells are only found in the lining of the anus. If left untreated, these cells may develop into invasive cancer.

T1 – The tumour is 2cm or smaller.

T2 – The tumour is larger than 2cm, but not bigger than 5cm.

T3 – The tumour is larger than 5cm.

T4 – The tumour can be of any size but it has begun to grow into nearby structures, such as the vagina, bladder or urethra (the tube that carries urine from the bladder).

N – Nodes

This describes whether there are any lymph nodes near the anus that have cancer in them. The ‘N’ may have an ‘X’ or a number written next to it:

NX – The lymph nodes were not examined.

N0 – The lymph nodes were examined but no cancer was found.

N1 – Cancer was found in the lymph nodes closest to the rectum (perirectal nodes).

N2 – Cancer was found in the lymph nodes in the groin (inguinal nodes) or pelvis (pelvic nodes) on one side of the body.

N3 – Cancer was found in either the rectal nodes and the nodes in the groin or pelvis OR in the 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.

Our cancer support specialists on 0808 808 00 00 can tell you more about TNM staging. It’s also important to talk to your doctor for detailed information about your situation.


Grading

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

Grade 1 (low-grade)

The cancer cells tend to grow slowly and look quite similar to normal cells (they are ‘well differentiated’). These cancers are less likely to spread than higher grade cancers.

Grade 2 (moderate-grade)

The cancer cells look more abnormal.

Grade 3 (high-grade)

The cancer cells tend to grow more quickly and look very abnormal (they are ‘poorly differentiated’). These cancers are more likely to spread than low-grade cancers.

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Treatment overview

Treatment depends on the stage of the cancer and where it is in the anus.