Classification of breast cancer is done on the basis of several grading systems. Each of these classifications can influence the prognosis and can affect the treatment response. We are listing the classifications as under:

  1. Histopathology: This form of classification is based on the histological appearance of the cancer. Most cancers occur in the epithelium lining the ducts or the lobules and are hence classified as ductal or lobular carcinoma.
  2. Grade: Grading compares the appearance of the normal breast tissue cells with that of the breast cancer cells. Normal cells in breast tissue are differentiated which implies they take up a certain unique and distinct shape as per their function. Cancerous cells lose their distinct appearance and the differentiation that is characteristic of healthy cells. The normal situation of cells lining the milk producing glands changes and the cancerous cells become disorganized. Cell division becomes haywire and the nucleus becomes less uniform. Pathologists classify cells as well differentiated (low grade), moderately differentiated (intermediate grade) and poorly differentiated (high grade) as the cells lose their normal features in the breast tissue.
  3. Stage: Breast cancer is also classified using the TNM system. It involves classification based on size of the tumour (T), whether the tumour has spread to the lymph nodes (N) and also if the cancer has metastasized (M) (Ie spread to far parts of the body). Larger size, nodal spread and metastasis will have more stage number and a bleaker prognosis.
  4. Receptor status: Breast cancer cells have receptors on their surface and also in their cytoplasm and nucleus. Changes in the cell chemistry occur when chemical messengers like hormones form bonds with the receptors. It is possible that that breast cancer cells may or may not have three important receptors: estrogen receptor, progesterone receptor and HER2. Cancer cells behave differently with each type of receptor. Sub classifications in this category are Hormone receptor positive, hormone receptor negative, HER2 positive, HER2 negative, Triple negative, and Triple positive. There are some other tests too that help in classification of breast cancers. One such test is test of ploidy and cell proliferation. Ploidy is the reference to amount of DNA contained in a cell. Normal DNA content makes a cell diploid while abnormal amount of DNA makes cells
  5. DNA assays: DNA testing provides information about the cancerous cells compared with normal cells. The specific changes observed in a breast cancer cell can help to classify the cancer.