The type of breast cancer that is diagnosed is determined by specific cells.

Ductal carcinoma in situ, or DCIS, also known as intraductal carcinoma, is when the abnormal cells have not spread through the ducts into surrounding breast tissue. It is a non-invasive breast cancer that has not spread outside of the breast; however, it can become invasive.

Lobular carcinoma in situ, also called lobular neoplasia, is when the abnormal cell growth starts in the lobules of the breast and has likely not spread to surrounding tissues. This subtype can be an indicator for the likeliness of developing invasive cancer in either breast.

Invasive ductal carcinoma, also known as infiltrating ductal carcinoma, is the most common type of breast cancer that occurs when the cancer starts in the ducts of the breast, then grows into fatty breast tissue. This type of breast cancer may spread to other parts of the body.

Invasive lobular carcinoma, also known as infiltrating lobular carcinoma, starts in the lobules of the breast. As one of the less common types, invasive lobular carcinoma may be difficult to detect via mammogram.

Inflammatory breast cancer, an uncommon type of invasive breast cancer, occurs when the cancer cells block the lymph vessels in the skin, causing inflammation, redness, pitted appearance, itchiness or tenderness. In this instance, a lump may not be detected

Paget disease, also rare, starts in the ducts and spreads to the skin of the nipple. Symptoms include crusted, scaly, red, bleeding, oozing, burning or itchy nipples.

Lastly, there are subtypes of breast cancer driven by hormones that will drive treatment decisions: hormone receptor-positive, HER2-positive and triple-negative breast cancer.