Reviewed by Joseph Maloney, M.D.
Breast cancer is the most common cancer among women, and the second leading cause of cancer death in the United States. While most breast lumps are caused by fibrocystic changes and are benign, breast cancer is a malignant tumor that develops from cells of the breast. The disease occurs mostly in women, but does occur rarely in men.
This year, there will be 215,000 new cases in the United States, and breast cancer will take the lives of 41,000 women.
Types of breast cancer include:
- Adenocarcinoma: This is a general type of cancer that starts in glandular tissues anywhere in the body. There are several subtypes of adenocarcinoma that account for nearly all breast cancers.
- Ductal carcinoma in situ (DCIS): Ductal carcinoma in situ is the most common type of noninvasive breast cancer. There are cancer cells inside the ducts but they do not spread through the walls of the ducts into the fatty tissue of the breast. Nearly 100 percent of women diagnosed at this early stage of breast cancer can be cured. The best way to find DCIS is with a mammogram.
- Infiltrating (or invasive) lobular carcinoma (ILC): ILC starts in the milk-producing glands. Similar to IDC, this cancer has the potential to spread (metastasize) elsewhere in the body. About 10% to 15% of invasive breast cancers are invasive lobular carcinomas. ILC may be more difficult to detect by mammogram than IDC.
- Inflammatory breast cancer: This rare type of invasive breast cancer accounts for about one percent of all breast cancers. It is an aggressive and fast-growing cancer. Inflammatory breast cancer makes the skin of the breast look red and feel warm, as if it were infected. The breast skin can develop a thick, pitted texture and/or ridges and small bumps that look like hives.
- In situ: This term is used for an early stage of cancer in which a tumor is confined to the immediate area where it began. Specifically in breast cancer, in situ means that the cancer remains confined to ducts or lobules.
- Lobular carcinoma in situ (LCIS): While not a true cancer, LCIS (also called lobular neoplasia) is sometimes classified as a type of noninvasive breast cancer. It begins in the milk-producing glands, but does not penetrate through the wall of the lobules. There is a higher risk of developing an invasive breast cancer in the same breast, or opposite breast. A physical exam two or three times a year, as well as an annual mammogram, are recommended
- Medullary carcinoma: This special type of infiltrating breast cancer has a relatively well-defined, distinct boundary between tumor tissue and normal tissue. It accounts for about five percent of breast cancers. The outlook, or prognosis, for this kind of breast cancer is better than for other types of invasive breast cancer.
- Mucinous carcinoma: This rare type of invasive breast cancer is formed by mucus-producing cancer cells. The prognosis for mucinous carcinoma is better than for the more common types of invasive breast cancer.
- Paget's disease of the nipple: This type of breast cancer starts in the breast ducts and spreads to the skin of the nipple and the areola, the dark circle around the nipple. It is a rare type of breast cancer, occurring in only 1% of all cases. The skin of the nipple and areola often appears crusted, scaly, and red, with areas of bleeding or oozing. The woman may notice burning or itching.
- Phyllodes tumor: This very rare type of breast tumor forms from the stroma (connective tissue) of the breast, in contrast to carcinomas that develop in the ducts or lobules. Phyllodes (also spelled phylloides) tumors are usually benign but on rare occasions may be malignant (having the potential to metastasize).
- Tubular carcinoma: Accounting for about 2% of all breast cancers, tubular carcinomas are a special type of infiltrating breast carcinoma. They have a better prognosis than usual infiltrating ductal or lobular carcinomas.
The Challenge of Dense Breast Tissue
Although mammography is the best tool to detect breast cancer in its early stages, it has limitations when it comes to dense breast tissue. Dense breasts occur in approximately 40 percent of women in the United States and Europe, and are most prevalent in women of Asian descent. In addition to making it more difficult to image, having dense breasts is a risk factor for breast cancer. Tissue is often classified by the BIRADS system – the American College of Radiology Breast Imaging Reporting and Data System. The four categories are as follows: (1) entirely fat; (2) scattered fibroglandular densities; (3) heterogeneously dense; and (4) extremely dense.
Ask your doctor what your breast density assessment is at your next physical exam.