Tumor Grade and Pathology

Breast Cancer Prognosis, Diagnosis and Treatment

Tumor grade is one of many items that will appear on your pathology report. This data helps your doctor decide on the most effective treatments for the best outcome. Breast cancer is graded using the Bloom-Richardson scoring system. Here's what you need to know.

Factors That Affect Treatment and Outcome

If you've had a breast biopsy and been diagnosed with breast cancer, you will need to know what treatments are best for you, and what your prognosis will be. A prognosis is your doctor's way of stating your best outcome after you've completed treatment. Many factors are considered in making an accurate diagnosis and treatment decisions -- the type of breast cancer, size of tumor, stage, hormone receptor status, lymph node involvement, and the tumor grade.

The Bloom-Richardson Grading System

There are several different systems for grading cancer. The Bloom-Richardson system is used for grading breast cancer, and has a scale of 1 - 3. A pathologist will take a sample of tissue from your tumor, and examine it under a microscope. Tumor cells that look most like normal cells are given a low grade, while those that look the most abnormal are given a high grade. High-grade tumors are fast-growing, spreading (metastatic), and aggressive. Knowing your tumor grade helps your doctor decide which treatments may be best for you.

The Tumor Grading Process

A pathologist looks at the tumor cells and checks for three microscopic features:

  • degree of tumor tubule formation (percentage of cancer composed of tubular structures)
  • tumor mitotic activity (rate of cell division)
  • nuclear grade (cell size and uniformity)

Each feature is scored on a scale of 1 - 3.

Cell Feature Scoring

The pathologist will assign a value to each feature of the cells, based on its activity. This is how the scores may be understood:

Feature Score 1: Slow cell growth rate
Feature Score 2: Intermediate cell growth rate
Feature Score 3: Fast cell growth rate

Feature Scores Add Up to Three Grades

Tumor Grade Table
Tumor Grade Table. Illustration by Pam Stephan

The score of all three features are added together for a total between 3 and 9.

Click on the table on the left to expand it and see how Feature Scores and Tumor Grades compare. Grade 1 is the least aggressive, while Grade 3 is the most aggressive type of tumor.

Doing the Math

Here is an example. If a tumor has these feature scores:

Tubule formation: 1
Mitotic activity: 2
Nuclear grade: 2

We add 1 + 2 + 2 = 5, which is given a Grade 1, the slowest growing, and least aggressive tumor type.

Tumors that are given a high grade and that contain dead cells (necrosis) are more likely to recur after treatment. High grade tumors will be treated more aggressively than low grade tumors.

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Article Sources
  • National Cancer Institute. Tumor Grade: Questions and Answers. Reviewed: 05/19/2004.
  • California Cancer Registry. Volume I: Data Standards and Data Dictionary. Bloom-Richardson Grade for Breast Cancer Updated May 2007.​