How do your cancer cells appear under a microscope?

When a sample of your breast cancer is examined under a microscope, here's what the pathologist looks for:

• Cancer cells with unique appearances. Some subtypes of breast cancer are named for the way they appear under the microscope. Subtypes include tubular, mucinous, medullary and papillary. Your subtype gives your doctor some clues about your prognosis and how your cells may respond to treatment.
• The degree of difference between the cancer cells and normal cells. How different your cancer cells look from normal cells is called your cancer's grade. Breast cancers are graded on a 1 to 3 scale, with grade 3 cancers being the most different looking and considered the most aggressive.