Understanding breast cancer
Breast cancer is a disease in which the breast cells of the lobules, ducts, or surrounding connective tissue begin to grow abnormally. Rapid division of these breast cells causes the formation of a breast lump or mass that grows and, in certain cases, metastasizes (spreads) to blood vessels, lymph nodes, or other areas of the body.
Breast cancer behavior, progression, and characteristics vary by type, with each requiring a specific approach to treatment and management. Our specialized breast pathologists use their in-depth understanding of tumor characteristics to recognize all types of breast cancer.
Breast cancer type is determined by two factors—where the cancer began and whether it has spread. Most breast cancers start in the breast ducts, which carry milk to the nipples (ductal cancers). Breast cancer may also begin in the breast lobules, the glands that produce milk (lobular cancers).
Breast cancer may also be non-invasive or invasive. Breast cancer is non-invasive if it has not spread to nearby breast tissue, whereas invasive (or infiltrating) breast cancers spread to surrounding connective tissue.
No matter where breast cancer originates in the breast, it can spread to other areas of breast tissue, lymph nodes under the armpit, or even to other parts of the body. When breast cancer has metastasized, it is considered in stage 4.
We test the cancer cells for hormone receptors and genetic expression. Depending on the results of those tests, we may use specialized therapies to further personalize your treatment.
- Hormone receptor status: Some breast cancers use the hormones estrogen and progesterone to grow. Those cancer cells have receptors that “feed” on the hormones. These tumors are considered hormone receptor-positive (HR+), or hormone-positive. About 80 percent of all breast cancers are HR+. Breast cancer may test positive for estrogen (ER+), progesterone (PR+), or both (ER/PR+).
- HER2 status: We typically test invasive breast cancer tissue for HER2, or human epidermal growth factor receptor 2. Normal breast tissue has HER2 receptors (produced by the HER2 gene) on each cell. These receptors control breast tissue growth and repair. In some cases, an excess of HER2 receptors causes cells to grow too rapidly, leading to a tumor.