Breast cancer is a disease in which cells in the breast grow out of control. While it occurs almost entirely in women, men can develop breast cancer as well. Rather than a single type of cancer, breast cancer is actually a group of many subtypes.
Types of Breast Cancer
Breast cancer can start in different parts of the breast: the glands, milk ducts, and fatty tissue. The glands, called lobules, produce milk, while the ducts carry milk to the nipple. The rest of the breast is made up of connective tissue and fat, which help support its structure.
Most breast cancers begin in the ducts, known as ductal cancers. Others start in the lobules and are called lobular cancers. Less common types of breast cancer can develop in other areas, such as the nipple, connective tissue, or the lining of blood and lymph vessels.
Hormone and HER2-Positive Breast Cancers
In addition to where breast cancer starts, your oncologist will also evaluate the cancer's hormone and HER2 status. About two-thirds of breast cancers are hormone receptor-positive, meaning they contain receptors for estrogen and/or progesterone on the surface of the cancer cells.
Some breast cancers are HER2-positive, meaning the cancer cells have receptors for the HER2 protein, which causes the cancer cells to grow.
You can have any combination of these, or have none of them, which is called triple-negative breast cancer.
Once your oncology team understands the receptor status, they can select treatments most likely to be effective. This information is provided in the pathology report after a biopsy.
Learn more about hormone receptors and HER2.
