Histology is the study of tissues, including cellular structure and function.
To determine a tumor's histologic grade, pathologists examine the breast cancer cells and their patterns under a microscope. A sample of breast cells may be taken from a breast biopsy , lumpectomy or mastectomy . The scores of each of the cells' features are then added together for a final sum that will range between 3 to 9. Cancers with a high grade, necrosis, cancers close to the surrounding margin of breast tissue of a lumpectomy sample, or large areas of DCIS are more likely to recur after breast cancer treatment than other breast cancers. Patients whose cancers have ER or PR-positive receptors tend to have a better prognosis than patients whose cancers do not have these receptors.