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Grading soft tissue sarcoma
Knowing the grade of soft tissue sarcoma gives your healthcare team an idea of how quickly the cancer may be growing and how likely it is to spread. Doctors also use the grade to help stage the tumour. This helps them plan your treatment. The grade can also help the healthcare team predict how you might respond to treatment.
To find out the grade of soft tissue sarcoma, the pathologist looks at a tissue sample from the tumour under a microscope. The grade that the pathologist gives is based on the following factors (mitotic index and necrosis are the most important):
- Mitotic index is the rate at which cancer cells are dividing.
- Necrosis is the amount of dead tissue within a tissue sample.
- Cellularity is the number and types of all cells in a given tissue sample.
- Histologic type is the type of cancer cell in a given tissue sample.
- Differentiation is how the cancer cells look and behave compared to normal cells.
- Pleomorphism is the degree of variation in size and shape of cancer cells in a tissue sample.
Experts have had difficulty reaching a consensus about what criteria should be included in grading soft tissue sarcomas. In addition, certain types of soft tissue sarcoma do not fit into any standard grading system. As a result, there isn’t a specific or standard criteria used to determine the grade at this time. The lack of a standard grading system for soft tissue sarcoma makes it difficult to compare treatment options or clinical trial results among differing treatment centres.
The following grading systems and scales are used with soft tissue sarcoma.
FNCLCC grading system
The French Federation of Comprehensive Cancer Centers (FNCLCC) system is most commonly used to grade soft tissue sarcomas. In this system, the grade is based on the following factors:
The cells are given a score of 1–3 based on how they look.
A score of 1 is given when the cancer cells look very similar to normal cells.
A score of 3 is given when the cells look very abnormal.
The cells are given a score of 1–3 based on how they are dividing.
A score of 1 is given when only a few cells are seen dividing.
A score of 3 is given when many cells are seen dividing.
The tumour is given a score of 0–2 based on how much of the tumour is made up of dying tissue.
A score of 0 is given where there is very little dying tissue present.
A score of 2 is given where there is a larger amount of dying tissue.
The scores for each factor are added up to determine the grade of the cancer. A higher score means a higher grade. A high-grade cancer tends to grow and spread faster than a low-grade tumour.
Grade cannot be assessed
Total score of 2 or 3
Total score of 4 or 5
Total score of 6 or higher
Memorial Sloan-Kettering Cancer Center grading system
Memorial Sloan-Kettering Cancer Center uses a 2-grade system.
The cancer is low grade.
The cancer is slower growing and less likely to spread than high-grade cancer.
The cancer is high grade.
The cancer is faster growing and more likely to spread than low-grade cancer.
AJCC grading system
The American Joint Committee on Cancer (AJCC) uses a 4-grade system. It is based on differentiation, or how much the cancer cells look and behave like normal cells.
Well-differentiated cancer cells look and behave almost like normal cells. They tend to be slower growing and spread slowly. Poorly differentiated or undifferentiated cancer cells don’t look or act like normal cells. They tend to grow and spread more quickly.
Grade cannot be assessed
Moderately well differentiated
Comparing grading systems
The following table shows how the grades of the different grading systems for soft tissue sarcoma compare.
|Memorial||FNCLCC grading system||AJCC grading system|
G1 (low grade)
G1 or G2
G2 (high grade)
G2 or G3
G3 or G4