There are different types of breast cancer that start in the cells lining the milk ducts (ductal carcinoma) or in the glands (called lobes) that produce the breast’s milk (lobular carcinoma). Some of these cancers can grow into other tissues in the breast or spread to other parts of the body. Breast cancer cells that spread to other parts of the body are called metastatic breast cancer.
Doctors divide breast cancers into subtypes based on how they look under a microscope. The type of breast cancer you have determines which treatment options may be best for you. For example, doctors can tell whether your cancer is a type of ductal or lobular carcinoma, which gives clues about how it might respond to certain treatments. Other subtypes of breast cancer include tubular, medullary and mucinous carcinoma.
Ductal carcinoma is the most common type of breast cancer. It grows in the cells that line the milk ducts. Ductal carcinoma in situ, or DCIS, is the earliest form of ductal carcinoma. DCIS does not usually grow or spread to other tissues.
Invasive ductal carcinoma accounts for about 80% of all breast cancers. It is a fast-growing cancer that can grow into the fatty tissue that surrounds the milk ducts, but it rarely spreads to other tissues or organs in the body. Invasive ductal carcinoma is found in women of all ages, though it is more common in post-menopausal women.
Invading lobular carcinoma is the second most common type of breast cancer. It grows into the breast’s lobules. Invasive lobular carcinoma is less common than invasive ductal carcinoma, but it is more likely to spread to other parts of the body.
Mucinous carcinoma is very rare and accounts for about 2% of all breast cancers. It grows in the cells that make milk and secrete a sticky fluid, called mucin. The mucin helps keep the cells moist. Cancer cells in this type of breast cancer have lots of mucin around them, which gives the tumors a gel-like appearance under a microscope.
There are also several other types of breast cancer that begin in the connective tissue made up of fat, muscle and blood vessels. These types of breast cancer are called sarcomas and are very rare. Examples of sarcomas that can occur in the breast include phyllodes tumor and angiosarcoma.
Some breast cancers can spread to other parts of the body, including the liver, bones and lungs. When this happens, it is known as metastatic breast cancer and is treated differently than localized breast cancer. If you have metastatic breast cancer, you may need to receive chemotherapy and/or hormone therapy in addition to surgery and radiation. These additional treatments are called adjuvant therapies. It is important to talk with your doctor about the goals of your care and choose a treatment plan together. This type of discussion is called shared decision-making and can help you feel confident in your choice of treatment. Your doctor can also help you understand your insurance coverage and how it might affect your options for care.
