Grade is a “score” that tells you how different the cancer cells’ appearance and growth patterns are from those of normal, healthy breast cells. Your pathology report will rate the cancer on a scale from 1 to 3:
- Grade 1 or low grade (sometimes also called well differentiated): Grade 1 cancer cells look a little bit different from normal cells, and they grow in slow, well-organized patterns. Not that many cells are dividing to make new cancer cells.
- Grade 2 or intermediate/moderate grade (moderately differentiated): Grade 2 cancer cells do not look like normal cells and are growing and dividing a little faster than normal.
- Grade 3 or high grade (poorly differentiated): Grade 3 cells look very different from normal cells. They grow quickly in disorganized, irregular patterns, with many dividing to make new cancer cells.
Having a low-grade cancer is an encouraging sign. But keep in mind that higher-grade cancers may be more vulnerable than low-grade cancers to treatments such as chemotherapy and radiation therapy, which work by targeting fast-dividing cells.
Be careful not to confuse grade with stage, which is usually expressed as a number from 0 to 4 (often using Roman numerals I, II, III, IV). Stage is based on the size of the cancer and how far it has (or hasn’t) spread beyond its original location within the breast.