Breast Cancer Grades

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

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

Grading breast cancer cells

Three cancer cell features are studied and each is assigned 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 tissue.
  • 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.

Necrosis (areas of dead or dying cancer cells) is also noted. If there is necrosis, it means the tumor is growing quickly.

  • The term comedocarcinoma is often used to describe DCIS with a lot of necrosis.
  • The term comedonecrosis may be used if a breast duct is filled with dead and dying cells.

Comedocarcinoma and comedonecrosis are linked to a higher grade of DCIS.

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

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.

Henry NL, Shah PD, Haider I, Freer PE, Jagsi R, Sabel MS. Chapter 88: Cancer of the Breast. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 6th ed. Philadelphia, Pa: Elsevier; 2020.

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.

Last Medical Review: September 20, 2019 Last Revised: September 20, 2019

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