Stages and grades of soft tissue sarcoma

How do doctors grade sarcoma?

The grade of a cancer tells you how much the cancer cells look like normal cells. This gives your doctor an idea of how the cancer might behave and what treatment you need. 

The grade is one of the things your doctors need to know to work out the stage of your sarcoma.

Your doctor takes a ​biopsy​ of the sarcoma. A specialist doctor called a ​pathologist​  looks at the biopsy under a microscope to grade it. The grade is based on 3 factors. The scores are added together to find the grade. These are:

• differentiation

• mitotic count

• necrosis

Differentiation

Differentiation means how different the sarcoma cells look under a microscope, compared to normal cells. The pathologist will grade the cells as 1, 2 or 3.

A score of 1 means cancer cells look similar to normal cells.

A score of 2 means cancer cells look moderately different to normal cells. The pathologist can see what type of sarcoma it is.

A score of 3 means cancer cells are abnormal and very different to normal cells. A score of 3 might mean it is difficult to be sure of the type of sarcoma it is.

Mitotic count

The pathologist looks at how many cells are dividing under the microscope. They give the cells a score of 1,2, or 3. This might show how fast the cancer is growing. 

A score of 1 means there are less than 10 cells dividing.

A score of 2 means there are more than 10, but less than 20 cells dividing.

A score of 3 means there are more than 20 cells dividing.

Necrosis

The pathologist looks at how much of the sarcoma is made up of dying tissue. The pathologist gives a score of 0, 1 or 2.

0 means there is no dying tissue (necrosis).

1 means that less than half (50%) of the cancer is dying tissue (necrosis).

2 means that more than half (50%) of the cancer is dying tissue (necrosis).

Grades

The scores for differentiation, mitotic count and necrosis are added together to give the grade.

Grade 1 means a total score of 2 or 3.

Grade 2 means a total score of 4 or 5.

Grade 3 means a total score of 6,7 or 8.

Your doctor may describe your sarcoma as low grade (grade 1) or high grade (grade 2 or 3).

Grade is important because it tells you how the cancer is likely to behave. A low grade cancer is likely to be slower growing and less likely to spread to another part of the body. A high grade cancer is likely to be faster growing and is more likely to spread than a low grade sarcoma.

The grade is one of the things your doctors need to know to work out the stage of your sarcoma.

Staging systems

There are different systems used in the UK to stage soft tissue sarcoma. The two main ways are the TNM system and number systems.

TNM stands for Tumour, Node, Metastasis.

The tumour (T) and number stages depend on where in the body the sarcoma is. The staging for node (N) and metastases (M) is the same, wherever your sarcoma is in the body.

The T stages on this page are for sarcoma in the arms or legs (extremities) or trunk. The trunk includes the chest, tummy (abdomen) and back. There are different T stages for:

• sarcoma in the head and neck

• sarcoma in the organs of the abdomen or chest

• sarcoma in the lining of the abdominal space behind the abdominal organs (retroperitoneum)

• sarcoma in the area behind the abdominal lining and organs (retroperitoneum)

• gastrointestinal stromal tumour (GIST)

• rare types of sarcoma

Your specialist can explain where your sarcoma is and what your stage means.

TNM stages of sarcoma in arms, legs, or trunk

Tumour (T)

T describes the size of the sarcoma (area of cancer). 

There are 4 main T stages. These are T1 to T4.

T1 means the cancer is smaller than 5cm.

T2 means the cancer is larger than 5cm, but no larger than 10cm.

T3 means the cancer is larger than 10cm, but no larger than 15cm.

T4 means the cancer is larger than 15cm.

Node (N)

N refers to your lymph nodes. These are a network of glands throughout the body, for example in your armpits and neck. They drain away waste fluid, waste products and damaged cells. They also contain cells that fight infection. 

N0 means one of the following:

• there are no cancer cells in the lymph nodes

• tests cannot show if there are cancer cells in the lymph nodes

N1 means there are cancer cells in at least 1 lymph node.

It is not common for soft tissue sarcomas to spread to lymph nodes.

Metastasis (M)

M describes whether the cancer has spread to a different part of the body.

There are 2 main stages - M0 and M1.

M0 means the cancer has not spread to other parts of the body.

M1 means cancer has spread to other parts of the body such as the lungs.

Number stages

There are 4 main stages in this system (stage 1 - 4).

Stage 1

1a means the cancer is smaller than 5cm and has not spread to the lymph nodes or other parts of the body. The cancer cells are grade 1, or cannot be assessed.

1b means the cancer is larger than 5cm and has not spread to the lymph nodes or other parts of the body. The cancer cells are grade 1, or cannot be assessed.

Stage 2

The cancer is smaller than 5cm and has not spread to the lymph nodes or other parts of the body. The cancer cells are grade 2 or 3.

Stage 3

3a means the cancer is between 5cm and 10cm, and has not spread to the lymph nodes or other parts of the body. The cancer cells are grade 2 or 3.

3b means the cancer is larger than 10cm and has not spread to the lymph nodes or other parts of the body. The cancer cells are grade 2 or 3.

Stage 4

Stage 4 means the cancer is advanced. It means the cancer is any size, the cancer cells are any grade, and one of the following:

• cancer has spread to the lymph nodes, but not to other parts of the body

• cancer has spread to other parts of the body, such as the lung and the lymph nodes may or may not contain cancer cells.

Read about treatment for soft tissue sarcoma