Grading ovarian cancer

The grade is a description of how the cancer cells look compared to normal cells and their growth rate. To find out the grade of ovarian cancer, the pathologist looks at a tissue sample from the tumour under a microscope.

How different the cancer cells are is described as differentiation.

Low grade usually means that the cancer cells are well differentiated. They look almost like normal cells. Lower grade cancer cells tend to be slow growing and are less likely to spread.

High grade usually means that the cancer cells are poorly differentiated or undifferentiated. They look less normal, or more abnormal. Higher grade cancer cells tend to grow more quickly and are more likely to spread than low-grade cancer cells.

Serous epithelial ovarian cancers are unique, in that the names of the 2 different tumour subtypes include the grade, based on their appearance and behaviour:

• LGSC – low-grade serous carcinoma
• HGSC – high-grade serous carcinoma

Some ovarian cancers are, by definition, high grade, such as clear cell carcinoma. Other types of ovarian cancer may be graded as 1, 2 or 3, such as endometrioid adenocarcinomas. A lower number means the cancer is a lower grade.

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.