There's not just one type of breast cancer. Ductal carcinoma and lobular carcinoma are the most common types. Both ductal and lobular carcinomas can be invasive or noninvasive breast cancer, which means the cancer cells have grown into adjacent tissues. It's important to know the type of breast cancer you have. That's a big factor in determining the type of treatment that will be best for you. Doctors diagnose the type of breast cancer with a combination of breast exam, mammogram, and breast biopsy. Ductal Carcinoma and Lobular Carcinoma The most common types of breast cancer start in a lobule or a duct. Lobules are glands in the breast that produce milk. Ducts are like tubes that carry the milk to the nipple. Ductal carcinoma is the most common. The word “carcinoma” means cancer that starts in cells that form linings. These are epithelial cells. Ductal carcinoma starts in the epithelial cells that line the milk ducts. There are two types: Ductal carcinoma in situ (DCIS). This is breast cancer that's only in the duct lining. Some types of DCIS progress and spread to other areas and other types don't. It's not possible to predict the course of DCIS. However, it's almost always curable. Treatment may include breast-conserving surgery like a lumpectomy followed by radiation. Invasive ductal carcinoma. This is cancer that started in a duct and has broken through the duct wall to involve other breast tissues. This cancer can spread (metastasize) beyond the breast. Treatment of invasive breast cancer depends on the stage of the cancer. That refers to how big the cancer is and how far it has spread. Treatment may include surgery, radiation or drugs (such as chemotherapy, hormone therapy, or targeted therapy like immunotherapy), or a combination of treatments. Lobular carcinoma starts in the glands of the breast that produce milk. Just as with ductal carcinoma, there are two types: Lobular carcinoma in situ (LCIS). With LCIS, cancer-like cells are only in the lining of a lobule. LCIS is not actually considered breast cancer because it doesn't spread. But, it increases the odds of developing invasive cancer in either breast. Because LCIS itself usually does not become invasive, you may not need treatment. Instead, you'll need more frequent checks for invasive breast cancer. You may also take medication to reduce your risk of developing invasive breast cancer. Invasive lobular carcinoma. This cancer starts in a lobule and can spread beyond it. Treatment depends on the stage of breast cancer. Less Common Types Less common types of breast cancer may behave differently than ductal or lobular breast cancers. They may need different treatments. The most common of these uncommon types are: Inflammatory breast cancer. This usually starts as invasive ductal cancer. Cancer cells spread to lymph vessels near the skin. These are tiny channels that carry a clear fluid called lymph. This type of cancer causes swelling of the breast. It may burn and feel heavy. The skin of your breast may become thick and pitted, like the skin of an orange. Treatment for inflammatory breast cancer usually starts with chemotherapy, followed by surgery and radiation. Paget’s disease of the nipple. This starts in a duct but spreads to the nipple. The nipple may bleed. The dark circle of skin around the nipple (areola) may become red and scaly. Treatment usually includes surgery to remove the breast. More rare types of breast cancer include those that start in blood vessels of the breast or in the tissue that holds the breast together, called connective tissue. There are also different subtypes within each of these. Once doctors suspect breast cancer or find something abnormal on a mammogram or other screening or exam, they perform a series of tests and procedures to determine the specific type, subtype and stage of breast cancer. Doctors tailor breast cancer treatment for each patient depending on the type and stage of breast cancer. Talk with your doctor about your type of breast cancer and about the best options for treatment.