breast cancer is the growth of abnormal cells in the ducts or lobes of the breast. breast cancer may be either:
- invasive.
- this means cancer has spread from the ducts or lobes into normal breast tissue. the main invasive types are:
- ductal carcinoma. this cancer starts in the ducts of the breast. it's the most common type of breast cancer.
- lobular carcinoma. this cancer starts in the lobes of the breast. it's the second most common type.
some breast cancer is a mix of ductal and lobular carcinoma. other less common invasive types include inflammatory breast cancer and male breast cancer.
- non-invasive.
- this means the abnormal cells haven't spread beyond the ducts or lobes. these cancers include:
- ductal carcinoma in situ (dcis). in this type, the abnormal cells are only in the ducts of the breast. (lobular carcinoma in situ [lcis] is not considered to be cancer.)
- paget disease of the nipple. the abnormal cells are only in or around the nipple. this is a rare type of cancer.
after the type of cancer is known, the cancer cells are checked for estrogen receptors, progesterone receptors, and large amounts of a protein called her2. this information helps a doctor plan the treatment.
if the cancer cells don't have these three traits, they are called "triple negative." triple-negative breast cancer is a less common type of invasive breast cancer.