Breast cancer types

When it comes to breast cancer, there are many ways used to describe and categorize it. They can be defined based on where the cancer starts. Most breast cancer types start in the milk lobules (glands in the breast that make milk) or in the milk ducts (tubes that carry milk from the lobules to the nipple).

Each of these breast cancer types are then divided by whether they are invasive (spread to other areas of the breast) or in situ (stay in their original location). Defining these characteristics produces the following four main types of breast cancer.

• Ductal carcinoma in situ (DCIS): Found in the milk ducts and hasn’t grown into other areas of the breast.
• Invasive ductal carcinoma (IDC): Found in the milk ducts and has spread to other breast tissues.
• Lobular carcinoma in situ (LCIS): Found in lobules and hasn’t grown into other areas of the breast. This is considered a breast condition, not a cancer.
• Invasive lobular carcinoma (ILC): Found in lobules and has spread to other breast tissues.

Invasive types of breast cancer are the most common. Invasive ductal carcinoma (IDC) is the most common breast cancer type among both women and men – it affects about 75% of people who are diagnosed. Invasive lobular carcinoma (ILC) is the next most common type.

Breast cancers rarely start in other areas of the breast, such as the muscles, fat or blood vessels.

Regardless of the type of breast cancer, it’s easier to cure if it’s caught early through a screening mammogram.

Other breast cancer types

In addition to where they start and whether they are invasive, breast cancer types may be described based on their appearance or shape or on other parts of the breast where they occur:

• Medullary carcinoma: A tumor that is soft and gray. The area of cancer may feel spongy instead of like a lump.
• Tubular carcinoma: These cancer cells are shaped like tubes and feel spongy instead of like a lump. They’re more likely after the age of 50.
• Breast papilloma: A rare, benign (non-cancerous) tumor that forms near the nipple in the milk ducts.
• Papillary carcinoma: This cancer has finger-like growths that stick out from the cells.
• Inflammatory breast cancer: A rare kind of breast cancer that makes the skin of the breast look inflamed. It’s aggressive and fast-growing and often has no tumor or lump. It’s one of the most serious kinds of invasive breast cancer.
• Angiosarcoma: Cancer that grows in the lining of blood vessels or lymph vessels. Occurs most in people older than 70.
• Paget’s disease: A rare cancer that affects the skin of the nipple and areola (the dark skin surrounding the nipple). The affected breast often has internal tumors.
• Metastatic breast cancer: Breast cancer that spreads to other parts of the body besides the breast tissues and nearby lymph nodes.

Testing breast cancer cells

When breast cancer cells are removed from the breast through a biopsy or surgery, a pathologist tests them for various properties. Some of the tests are genetic. Breast cancer may be related to mutations in several genes, including BRCA1 (Breast Cancer gene one) and BRCA2 (Breast Cancer gene two).

The results of such tests can apply to any of the types of breast cancer listed above and will guide your provider’s recommendations about what treatment will be best for you.

Hormone receptor status

Breast cancer cells are checked to see if they respond to the hormones estrogen and progesterone because they make cancer cells grow faster. Results are categorized as:

• Estrogen receptor-positive (ER-positive)
• Progesterone receptor-positive (PR-positive)
• Estrogen receptor-negative (ER-negative)
• Progesterone receptor-negative (PR-negative)

Most newly diagnosed breast cancers test positive for reactions to estrogen or progesterone.

HER2 status

Breast cancers are also tested for the presence of a protein known as HER2. Based on the results, they’ll be described as either HER2-positive or HER2-negative.

Combined breast cancer status

If breast cancer cells test positive for estrogen, progesterone and HER2 they’re referred to as triple positive breast cancer. Such cancers can be treated with medications that target hormone receptors and HER2 proteins.

If breast cancer cells test negative for all three they’re called triple negative breast cancer. Triple negative breast cancer is considered one of the most serious kinds of breast cancer. It resists some of the most common breast cancer treatments. It can be treated with chemotherapy.