There are several types of breast cancer. The more common forms are carcinoma in situ, ductal carcinoma in situ, lobular carcinoma in situ, invasive ductal carcinoma, and invasive lobular carcinoma.

Carcinoma in situ is early stage cancer. At this point, it has not invaded the surrounding tissues of the breast nor other organs or tissue in the body. The cancer is only in the place where it began.

Ductal carcinoma in situ is the most common type of non-invasive breast cancer according to the American Cancer Society. Known as DCIS, this cancer is one of the most curable types of breast cancer. DCIS is confined to the ducts, has not spread to the breast tissue, and can be discovered early with a mammogram.

Lobular carcinoma in situ begins in the lobules or glands where milk is produced. LCIS is not truly cancer, but increases a woman's risk of getting invasive breast cancer in the future by 25%, and may warrant additional screening.

Invasive ductal carcinoma (IDC) is the most common form of invasive breast cancer. Starting in a milk duct, it invades the breast through the wall of the duct, and can spread to other parts of the body. IDC is responsible for approximately 80% of invasive breast cancers.

Invasive lobular carcinoma starts in the milk glands (the lobules). Like IDC, it can spread to other parts of the body and accounts for approximately 10% of all diagnosed breast cancers.

References and Other Resources:

American Cancer Society Overview: Breast Cancer, "What Is Breast Cancer?" American Cancer Society

Imaginis: The Women's Health Resource, "What is Breast Cancer?" Imaginis