The two main categories of breast cancer are invasive and noninvasive. Noninvasive breast cancers stay within the milk ducts and lobules (milk-producing glands) of the breast. Most breast cancers are invasive. They spread beyond these areas and invade healthy tissue.
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The most common noninvasive type of breast cancer is ductal carcinoma in situ (DCIS), in which cancer develops in the ducts that carry milk to the nipple but does not spread beyond those ducts.
A similar condition, lobular carcinoma in situ, begins in the lobules and does not grow any further. Unlike DCIS, LCIS is not considered a cancer, but if you have it, you have a higher risk of developing breast cancer.
Invasive Ductal Carcinoma: The Most Common Type of Breast Cancer
The most common form of breast cancer is invasive ductal carcinoma (IDC), sometimes also called infiltrating ductal carcinoma. About 80 percent of all breast cancers are IDC, and the risk of getting IDC increases as you grow older.
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IDC starts in the ducts just as DCIS does but then grows beyond the ducts and invades the surrounding healthy tissue inside the breast. Without treatment, the cancer can metastasize, or spread, into the lymph nodes and other areas of the body.
The options available to treat IDC depend in part on the stage of the cancer, as well as other factors, including the grade of the cancer.
Breast Cancer Stages: What Do They Mean?
Stages are numbers used to describe how far a cancer has advanced and where it has spread in the body. Cancer that has not spread beyond the breast is considered local.
Regional cancer has spread into the lymph nodes, mostly those in the armpit. When cancer spreads to other parts of the body, it is considered distant, since it exists far away from the breasts.
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Your prognosis, or your long-term outcome, relies heavily on what stage your cancer is. Cancer stages are often broken down further into subcategories to provide more specific information.
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Staging previously relied only on the size of the tumor and whether it had grown into surrounding tissue, whether the cancer was in the lymph nodes, and whether it had spread to other parts of the body beyond the breast.
