The Bloom-Richardson grade (BR grade) is a a histologic grade assigned by pathologists to breast cancers. It is the most common type of cancer grade system currently used. It is a semi-quantitative grading method based on three morphologic features of invasive breast cancers. The morphologic features that are used are:

1. degree of tumor tubule formation (percentage of cancer composed of tubular structures)
2. tumor mitotic activity (rate of cell division)
3. nuclear pleomorphism of tumor cells (nuclear grade, change in cell size and uniformity)

Each of these features is assigned a score ranging from 1 to 3. The scores are then added together for a final sum that will range between 3 to 9. This value is then used to grade the tumor as follows :

• 3-5 Grade 1 tumor (well-differentiated).
• 6-7 Grade 2 tumor (moderately-differentiated).
• 8-9 Grade 3 tumor (poorly-differentiated).

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