How do the cancer cells look under a microscope?

When looking at the breast cancer cells with a microscope, the pathologist looks for:

• Cancer cells with unique appearances. Some subtypes of breast cancer are named for the way they look under the microscope. Subtypes include tubular, mucinous, medullary and micropapillary. Your subtype gives your healthcare team some clues about your prognosis and how your cells may respond to treatment.
• Differences between the cancer cells and healthy cells. How different the cancer cells look from healthy cells is called the cancer's grade. Breast cancer grades go from 1 to 3. A grade 1 breast cancer has cells that look a little different from healthy cells. It generally means the cancer is likely to grow more slowly. A grade 3 breast cancer has cells that look very different from healthy cells. It generally means that the cancer is more likely to grow quickly.