Tumor grade is a way of classifying tumors based on certain features of their cells. The grade of a tumor 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
- How many of the cancer cells are in the process of dividing
The more the cancer cells look like normal cells, the lower the tumor grade tends to be. Also, the fewer cancer cells that are in the process of dividing, the more likely it isthat the tumor is slow-growing, which contributes to a lower tumor grade. Together, both of these factors determine the tumor grade.
These 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. Learn more about other factors that affect prognosis.