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Grades of breast cancer
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.
- tubule formation – the percentage of the tumour that is made up of tubular structures
- 1 – The tumour is made up of more than 75% tubules.
- 2 – The tumour is made up of 10%–75% tubules.
- 3 – The tumour is made up of less than 10% tubules.
- nuclear pleomorphism – the degree of change in the size and shape of the tumour cells’ nuclei (the part of the cell that holds the chromosomes, which contain genetic information)
- 1 – The nuclei are small and uniform in size and shape.
- 2 – The nuclei are medium to large in size, but are mostly the same size and shape.
- 3 – The nuclei are large and vary in size and shape.
- mitotic count – the number of cells that are actively dividing
- 1 – The tumour cells are dividing at a slow rate.
- 2 – The tumour cells are dividing at a moderate rate.
- 3 – The tumour cells are dividing at a fast rate.
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
Grading of ductal carcinoma in situ (DCIS)
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.
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