Tumor Grade

Tumor grade is a way of classifying tumors based on certain features of their cells. It is directly linked to prognosis.

Using a microscope, a pathologist studies the tumor tissue removed during a biopsy to check:

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 that are in the process of dividing, the more likely it is that the tumor is slow-growing, and the lower the tumor grade tends to be.)

Together, these two factors determine the tumor grade.

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 also impact survival and for any given tumor grade, survival varies greatly depending on these factors.