Grading is a way of classifying breast cancer cells based on their appearance and behaviour when viewed under a microscope. To find out the grade of a tumour, the biopsy sample is examined under a microscope. A grade is given based on how the cancer cells look and behave compared with normal cells (differentiation). This can give the healthcare team an idea of how quickly the cancer may be growing and how likely it is to spread.
Grading plays an important part in planning breast cancer treatment and can also be used to help estimate the prognosis (future outcome).
The most common grading system for breast cancer is the Nottingham modification of the Bloom-Richardson scale (may also be called the Scarff-Bloom-Richardson or the Elson-Ellis grade). It is used for invasive breast cancers (cancers that have spread beyond their original site into surrounding tissues).
This grading system is based on 3 different features of the cells in the tumour. Each of these features is given a score of 1 to 3.
The individual scores from these 3 features are added together to give a total score between 3 and 9. A tumour grade is then assigned based on the total score.
Low-grade (well-differentiated) tumours that do not appear to be growing quickly and are less likely to spread
Intermediate-grade (moderately differentiated) tumours that have features between grade 1 and 3
High-grade (poorly differentiated) tumours that tend to grow faster and are more likely to spread
Ductal carcinoma in situ (DCIS) may be given a grade based on the appearance of the nuclei and the presence of dead or dying cancer cells (necrosis).
Low grade (1)
The abnormal cells are small to medium in size, but are even in shape. There is no necrosis in the cells.
Intermediate grade (2)
The abnormal cells are small to medium in size, but are even in shape. There are areas of necrosis.
High grade (3)
The abnormal cells are large and uneven in size. There may or may not be any necrosis.