What is Breast Cancer
Front view diagram of healthy breast
Side view diagram of healthy breast
According to the American Cancer Society, approximately 207,090 new cases of invasive breast cancer were diagnosed in women in 2010. After increasing for more than two decades, female breast cancer incidence rates decreased by about two percent per year from 1998 to 2007, likely due to the reduced use of hormone replacement therapies as well as improved prevention, detection and treatment efforts.
There are two primary types of breast cancer, non-invasive and invasive breast cancer:
Non-Invasive
- Ductal carcinoma in situ (DCIS) - the most common type of non-invasive breast cancer, DCIS begins in the lining of the milk ducts, is composed of cells that have malignant features, but has not yet spread to other parts of the body. However, DCIS is considered a precursor to invasive breast cancer, and can develop into breast cancer if not treated.
- Lobular carcinoma in situ (LCIS) - the second most common non-invasive condition, LCIS develops in the milk lobules (milk-producing glands) and can be a risk marker for future breast cancer, but is not a direct pre-cursor.
Invasive Breast Cancer
- Invasive ductal carcinoma (IDC) - the most common type of breast cancer affecting women today, IDC originates in the lining of milk ducts and then penetrates the duct walls into surrounding breast tissue. This invasive characteristic identifies cancer cells that may spread to other parts of the body.
- Invasive lobular carcinoma (ILC) - ILC is the second most frequent type of invasive breast cancer, and accounts for about 10 to 15% of all invasive breast cancers. ILC originates in the milk-producing glands, or lobules, of the breasts, and similar to IDC, has the capacity to spread to other parts of the body.
Subtypes of invasive breast cancer include:
- Endocrine-sensitive breast cancer - any form of breast cancer where cells contain measurable amounts of the estrogen or progresterone receptor, making the tumor amenable to treatment with various endocrine interventions.
- Her2 positive breast cancer - any form of invasive breast cancer where cells contain an overabundance of the Her2 receptor, making the tumor amenable to treatment with specific anti-Her2 targeted therapies (such as trastuzumab/Herceptin).
- Triple negative breast cancer - a form of breast cancer that does not have estrogen receptors and progesterone receptors, and does not have an excess of the HER2 receptor on the cancer cell surface. This kind of cancer can be harder to treat because of a lack of agents that can target the cancer cell.
- Inflammatory breast cancer - a form of invasive breast cancer in which usually there is no lump or tumor. The skin of the breast feels warm, and looks red, thick and pitted, much like an orange peel.
- Medullary carcinoma - a less common subtype of IDC, the name for this cancer comes from the soft, fleshy tumor that resembles a part of the brain called the "medulla."
- Metaplastic carcinoma - a rare type of invasive breast cancer in which a portion of the cells in the tumor have changed into an alternate type of breast cancer (a mixed tumor).
- Mucinous carcinoma - a less common subtype of IDC, tumors for this cancer create thick pools of mucin (one of the main components in saliva).
- Papillary carcinoma - a rare subtype of IDC, this cancer usually forms in distinct lumps that have finger-like extensions projecting outwards.
- Tubular carcinoma - a less common subtype of IDC, this cancer is made up of collections of small tube-like cells (usually less than 1.0 cm in diameter).
- Paget's Disease - any of the above forms of breast cancer that directly involves the nipple.
- Male breast cancer - a rare form of breast cancer, with less than one percent of all breast carcinomas occuring in men. In 2010, it is estimated that 1,970 men were diagnosed with breast cancer. Breast cancer usually presents as a new lump or mass in a man's breast. While many facilities treat this with mastectomy, Stanford has successfully treated male breast cancer with lumpectomy.
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