When cells in the breast tissue grow and divide out of control, breast cancer is the result. When normal cell regulators malfunction and cells do not die at the normal rate, a failure of apoptosis, or unprogrammed cell death, occurs and cell growth proceeds unchecked. Cancerous tumors in the breast normally grow slowly. By the time a lump is palpable, sometimes it has been growing for as long as 10 years. Early diagnosis is the best way to decrease the risk of death from breast cancer. Monthly breast exams, mammography and clinical breast exams are good avenues to early diagnosis. In 2007, nearly 203,000 women in the United States were diagnosed with breast cancer and over 40,000 women died from it that year.
Non-Invasive Breast Cancer
Ductal carcinoma in situ, or DCIS, is the most common type of non-invasive breast cancer. In this case the cancer cells remain inside the ducts and have not spread through the duct walls into the surrounding tissue. DCIS accounts for about 1 in 5 new breast cancer cases, according to the American Cancer Society. If tumor necrosis, an area of dead or dying cancer cells, is present, the tumor is probably more aggressive. Comedocarcinoma is the term for DCIS with necrosis.
Lobular carcinoma in situ, or LCIS, is not considered a true cancer, but is sometimes classified as a type of non-invasive breast cancer because it begins in the milk-producing glands but does not grow through the wall of the lobules. Women with LCIS are at higher risk of developing an invasive breast cancer in the same or other breast.
Invasive Breast Cancer
If a breast cancer tumor is invasive, it has spread from the original site of either the milk ducts or lobules into nearby breast tissue and possibly into the lymph nodes or other parts of the body. These cancers usually have a poorer prognosis than DCIS.
Invasive ductal carcinoma is the most common type of breast cancer tumor, which accounts for 50 to 75 percent of breast cancers, according to the Susan B. Komen website. It begins in a milk duct, then invades the duct wall and begins growing in the fatty tissue of the breast. It may be able to spread to other parts of the body through the lymphatic system and bloodstream.. The next most common type is invasive lobular carcinoma, accounting for 10 to 15 percent of cases. It starts in the lobules and can spread to other parts of the body as well.
Less Common Breast Cancer Types
About one to three percent of all breast cancers are an uncommon type called inflammatory breast cancer. Inflammatory breast cancer, or IBC, causes the skin of the breast to look red and feel warm to the touch. It gives the breast a thick, pitted appearance, due to cancer cells blocking lymph vessels in the skin. In its early stages, IBC can be mistaken for a breast infection called mastitis. This type cancer has a higher chance of metastasis and worse prognosis than invasive ductal or lobular cancer.
Triple-negative breast cancer is used to describe cancers without estrogen and progesterone receptors and without an excess of the HER2 protein on their surfaces.They occur more in younger women and African-American women, tend to grow and spread more quickly than other types of breast cancer.
Mixed tumors contain more than one cell type.
Medullary carcinoma accounts for three to five percent of breast cancers and has a better prognosis than more common types of invasive breast cancer. It has a well-defined boundary between tumor tissue and normal tissue and its cells are large.
Paget disease of the nipple starts in the breast ducts, then spreads to the skin of the nipple, then the areola. Only accounting for about one percent of breast cancer cases, it is rare. The skin of the nipple and areola often are crusted, red and scaly with areas of oozing or bleeding.
Other less common cancers include metaplastic carcinoma, mucinous carcinoma, tubular carcinoma, papillary carcinoma, adenoid cystic carcinoma, phyllodes tumor and angiosarcoma.
"Disease Prevention and Treatment"; Life Extension Foundation; 2003.
American Cancer Society: https://www.cancer.org/Cancer/BreastCancer/DetailedGuide/breast-cancer-what-is-breast-cancer
Susan G. Komen for the Cure: https://ww5.Komen.org/BreastCancer/TypesofTumors.html
Centers for Disease Control and Prevention: https://www.cdc.gov/cancer/breast/statistics