The most common types of breast cancer are:
Invasive (or infiltrating) ductal carcinoma. This cancer starts in the milk ducts of the breast. Then it breaks through the wall of the duct and invades the fatty tissue of the breast. This is the most common form of breast cancer, accounting for 80% of invasive cases.
Ductal carcinoma in situ (DCIS) is ductal carcinoma in its earliest stage (stage 0). “In situ” refers to the fact that the cancer hasn’t spread beyond its point of origin. In this case, the disease is confined to the milk ducts and has not invaded nearby breast tissue. If untreated, ductal carcinoma in situ may become invasive cancer. It is often curable.
Infiltrating (invasive) lobular carcinoma. This cancer begins in the lobules of the breast where breast milk is produced, but has spread to surrounding tissues or other parts of the body. It accounts for about 10% of invasive breast cancers.
Lobular carcinoma in situ (LCIS) is cancer that is only in the lobules of the breast. It isn’t a true cancer, but serves as a marker for the increased risk of developing breast cancer later. Thus, it is important for women with lobular carcinoma in situ to have regular clinical breast exams and mammograms.
In addition, there are several other less common types of breast cancer.