Breast Cancer Grade
Knowing a breast cancer’s grade is important to understand how fast it’s likely to grow and spread.
What is a breast cancer’s grade?
Cancer cells are given a grade when they are removed from the breast and checked in the lab. The grade is based on how much the cancer cells look like normal cells. The grade 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.
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- References
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.
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Jagsi R, King TA, Lehman C, Morrow M, Harris JR, Burstein HJ. Chapter 79: Malignant Tumors of the Breast. In: DeVita VT, Lawrence TS, Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg’s Cancer: Principles and Practice of Oncology. 11th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2019.
Tomlinson-Hansen S, Khan M, Cassaro S. Breast Ductal Carcinoma in Situ. In: StatPearls. Treasure Island (FL): StatPearls Publishing; July 25, 2021. Accessed August 31, 2021.
Last Revised: November 8, 2021
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