Types of Breast Cancer
Breast cancer isn’t just one disease. There are many different types of breast cancer, each of which behaves differently, or develops in a different part of the breast. Breast cancers can occur in women, men, and nonbinary people, since everyone has breast tissue.
After you have a biopsy or surgery to remove breast cancer from your breast or lymph nodes, a doctor called a pathologist tests the tissue that was removed. These tests provide important information about the cancer, including what type of cancer it is. You can read about the results of the tests in your pathology report and discuss them with your doctor. Knowing the type of breast cancer you’ve been diagnosed with helps you and your doctor choose the best treatments for you.
Most breast cancers begin either in the ducts (the passages that connect the lobules to the nipple) or in the lobules (milk-producing glands). Breast cancers may also develop in breast tissues other than the ducts or lobules, particularly in the connective tissues and blood vessels in the breast, but these types are far less common.
Breast cancers are categorized as either invasive or non-invasive, depending on how they’ve grown. Breast cancer is called invasive (or infiltrating) when it has spread from the ducts or lobules into the surrounding breast tissue. When it’s called non-invasive (or in situ) it means it has not spread beyond the ducts or lobules. Non-invasive breast cancers are also called precancers or stage 0 cancers.
Whether they’re invasive or noninvasive, all breast cancers are always tested for the presence of estrogen and progesterone receptors. Invasive cancers will also be tested for the presence of an excess amount of HER2 proteins.
Within these categories, there are many types of breast cancers.
Invasive ductal carcinoma (IDC)
Invasive ductal carcinoma (IDC) is invasive breast cancer that starts in the milk ducts — the tubes that carry milk from the lobules to the nipple. It's the most common type of breast cancer.
Invasive lobular carcinoma (ILC)
Invasive lobular carcinoma (ILC) is invasive breast cancer that starts in the lobules, the glands in the breast that produce milk. It's the second most common type of breast cancer.
Ductal carcinoma in situ (DCIS)
Ductal carcinoma in situ (DCIS) is non-invasive breast cancer that has not spread outside the milk ducts where it started. DCIS isn’t life-threatening but is considered a precursor to invasive breast cancer and increases the risk of developing invasive breast cancer later in life.
Triple-negative breast cancer (TNBC)
Triple-negative breast cancer is an aggressive type of invasive breast cancer that tests negative for estrogen receptors and progesterone receptors and doesn’t have extra HER2 proteins.
Triple-positive breast cancer
Triple-positive breast cancer tests positive for estrogen receptors and progesterone receptors and has too many HER2 proteins. Triple-positive breast cancer is usually invasive, but sometimes it can be non-invasive.
Metastatic breast cancer
Metastatic breast cancer, also called stage IV breast cancer, is invasive breast cancer that has spread (metastasized) to parts of the body away from the breast, such as the bones, liver, lungs, or brain. Some people are initially diagnosed with metastatic disease; this is called de novo metastatic breast cancer. Others are first diagnosed with early-stage breast cancer and then, months or years after their original treatment, are diagnosed with metastatic breast cancer — this is called metastatic or distant recurrence.
Micrometastases
Micrometastases are tiny groups of breast cancer cells that have traveled from the breast to some other area of the body, particularly to the lymph nodes under the arm. Doctors look for micrometastases in the lymph nodes in the breast area because research shows micrometastases mean the breast cancer has a higher risk of spreading and may need different treatments than breast cancer without micrometastases.
Inflammatory breast cancer
Inflammatory breast cancer is a rare and aggressive type of invasive breast cancer. It occurs when cancer cells block lymph vessels in the skin of the breast, causing redness, swelling, and inflammation.
Paget disease
Paget disease of the breast is a form of breast cancer where cancer cells collect in or around the nipple. In some cases, it may be contained in the nipple and areola and considered non-invasive (stage 0). But in other cases, it’s accompanied by invasive breast cancer in the same breast.
Breast angiosarcoma
Breast angiosarcoma is a rare type of cancer that starts in the cells lining the blood or lymph vessels of the breast.
Male breast cancer
Male breast cancer is rare, but it does happen. Most breast cancers in men are invasive ductal carcinomas and are hormone receptor-positive.
Cancerous phyllodes tumors of the breast
Unlike most other breast tumors, phyllodes tumors of the breast first develop in the connective (stromal) tissue of the breast. Most phyllodes tumors are benign (not cancerous), but about 25% are cancerous.
Fungating tumors of the breast
Fungating breast tumors are tumors that grow through the skin of the breast. Only about 2% to 5% of locally advanced breast cancers — where the tumor has spread outside the breast — will develop into fungating breast wounds. Any type of invasive breast cancer can potentially become fungating.
