The Who, What, Where, When and Sometimes, Why.

Tumor Grade

What is tumor grade?

Tumor grade is a way of classifying tumors based on certain features of their cells. It’s highly related to prognosis and is part of breast cancer staging.

Using a microscope, a pathologist studies the tumor tissue removed during a biopsy and checks:

  • How much the cancer cells look like normal cells (The more the cancer cells look like normal cells, the lower the tumor grade tends to be.)
  • How many of the cancer cells are in the process of dividing (The fewer cancer cells in the process of dividing, the lower the tumor grade tends to be. This means the tumor is also more likely to be slow-growing.)

Together, these factors determine the tumor grade.

Tumor grades

Tumor grades are usually classified as:

Grade 1. The tumor cells look the most like normal tissue and are slow-growing (well-differentiated).

Grade 2. The tumor cells fall somewhere in between grade 1 and grade 3 (moderately-differentiated).

Grade 3. The tumor cells look very abnormal and are fast-growing (poorly-differentiated).

For any given tumor size and breast cancer stage, prognosis is poorer with a higher tumor grade.

Many other factors impact survival. For any given tumor grade, survival varies greatly depending on these factors.

Learn about tumor grade and breast cancer staging.

Learn more about other factors that affect prognosis. 

Updated 12/12/20

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Fact Sheet

Fact Sheet