Breast Cancer Grade

Cancer cells are given a grade when they are removed from the breast and checked in the lab. Knowing a breast cancer’s grade helps your cancer care team understand how fast it is likely to grow and spread.

What is a breast cancer’s grade?

When cancer cells are removed from your breast, they are checked in the lab and given a grade. This grade is based on how much the cancer cells look like normal cells. It is used to help predict your outcome (prognosis) and to help figure out what treatments might work best.

A low grade number (grade 1) usually means the cancer is slower-growing and less likely to spread.

A high grade number (grade 3) means a faster-growing cancer that’s more likely to spread.

An intermediate grade number (grade 2) means the cancer is growing faster than a grade 1 cancer but slower than a grade 3 cancer.

Grading invasive breast cancer cells

Three features of the invasive breast cancer cell are studied and each is given a score. The scores are then added to get a number between 3 and 9 that is used to get a grade of 1, 2, or 3, which is noted on your pathology report. Sometimes the terms well differentiated, moderately differentiated, and poorly differentiated are used to describe the grade instead of numbers:

• Grade 1 or well differentiated (score 3, 4, or 5). The cells are slower-growing, and look more like normal breast cells.
• Grade 2 or moderately differentiated (score 6, 7). The cells are growing at a speed of and look like cells somewhere between grades 1 and 3.
• Grade 3 or poorly differentiated (score 8, 9). The cancer cells look very different from normal cells and will probably grow and spread faster.

Our information about pathology reports can help you understand details about your breast cancer.   

Grading ductal carcinoma in situ (DCIS)

DCIS is also graded on how abnormal the cancer cells look and has a similar grading system to that used for invasive breast cancer (see above).

• Grade 1 or low grade DCIS. The cells are growing slower, and look more like normal breast cells. These cells tend to have estrogen and progesterone receptors (ER-positive and PR-positive). 
• Grade 2 or intermediate grade. The cells are growing at a speed of and look like cells somewhere between grades 1 and 3.
• Grade 3 or high grade. The cancer cells look very different from normal cells and are growing faster. These cells tend not to have estrogen and progesterone receptors (ER-negative and PR-negative). High grade DCIS is often more likely to turn into invasive breast cancer.

Necrosis (areas of dead or dying cancer cells) is also noted. If there is necrosis, it means the tumor is growing quickly. The term comedo necrosis may be used if a breast duct is filled with dead and dying cells. Comedo necrosis is often linked to a high grade of DCIS and has a higher chance of developing into invasive breast cancer.

See Understanding Your Pathology Report: Ductal Carcinoma In Situ for more on how DCIS is described.