Breast Cancer Grading


Modified Bloom-Richardson Grading System

How it works:

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Point-Scoring System

The tumor should be graded based on the representative portion of tumor (not the least differentiated part). Three factors are assessed when determining the grade:

  1. Tubule formation: How much of the tumor tissue has normal breast (milk) duct structures. 

    • Tubules must have clear central lumina to be counted​

  2. Nuclear grade: An evaluation of the size and shape of the nucleus in the tumor cells. 

    • Evaluate the “ugliest” area of tumor for nuclear pleomorphism

  3. Mitotic rate: How many dividing cells are present, which is a measure of how fast the tumor cells are growing and dividing. ​

    • Assess mitotic count in the most active part of the tumor.

    • You should count at periphery of tumor.

    • Need to assess 10 high powered fields, but they don’t have to have 10 contiguous fields

Overall Tumor Grade



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