Grading bone cancer

Grading describes how the cancer cells look compared to normal, healthy cells. Knowing the grade gives your healthcare team an idea of how quickly the cancer may be growing and how likely it is to spread. This helps them plan your treatment. The grade can also help the healthcare team predict future outcomes (your prognosis) and how the cancer might respond to treatment. The grade is also used to stage bone cancer.

To find out the grade of bone cancer, a pathologist looks at a tissue sample from the bone under a microscope. They look at how different the cells look from normal cells (called differentiation) and other features of the tumour such as the size and shape of the cells and how the cells are arranged. They can usually tell how fast a tumour is growing by looking at how many cells are dividing.

The pathologist uses a 2-grade or 3-grade system.

The 2-grade system describes the cancer as low or high grade.

Low-grade cancers have cancer cells that are well differentiated. The cells are abnormal but look a lot like normal cells and are arranged a lot like normal cells. Lower-grade cancers tend to grow slowly and are less likely to spread.

High-grade cancers have cancer cells that are poorly differentiated or undifferentiated. The cells don’t look like normal cells and are arranged very differently. Higher-grade cancers tend to grow more quickly and are more likely to spread than low-grade cancers.

The 3-grade system uses numbered grades. A lower number means the cancer is a lower grade.

Grade 1 cancers have cancer cells that are well or moderately well differentiated or low grade.

Grade 2 cancers have cancer cells that are poorly differentiated or high grade.

Grade 3 cancers have cancer cells that are undifferentiated or high grade.