NIH - Medical Encyclopedia Breast cancer

"There are several different types of breast cancer. Ductal carcinoma begins in the cells lining the ducts that bring milk to the nipple and accounts for more than 75% of breast cancers. Lobular carcinoma begins in the milk-secreting glands of the breast but is otherwise fairly similar in its behavior to ductal carcinoma. Other varieties of breast cancer can arise from the skin, fat, connective tissues, and other cells present in the breast. … Some women have what is known as HER2-positive breast cancer. HER2, short for human epidermal growth factor receptor-2, is a gene that helps control cell growth, division, and repair. When cells have too many copies of this gene, cell growth speeds up. It’s believed that HER2 plays a key role in turning healthy cells into cancerous ones. Some women with breast cancer have too much HER2, and are therefore considered HER2-positive. … Some families appear to have a genetic tendency for breast cancer. Two variant genes have been found that appear to account for this: BRCA1 and BRCA2. … The body's reduced ability to get rid of abnormal cells leads to damage that gradually accumulates. Women carrying mutated BRCA1 and/or BRCA2 genes start with pre-existing dysfunction of this system and have a "head start" in this damaging process. Hormones are important because they encourage cell growth. High levels of hormones during a woman's reproductive years, especially when they are not interrupted by the hormonal changes of pregnancy, appear to increase the chances that genetically damaged cells will grow and cause cancer."

Types of breast cancer

Breast lumps: Types of lumps and what they mean

Highlighted Articles

Mammographic Breast Density as a General Marker of Breast Cancer Risk (Cancer Epidemiology Biomarkers & Prevention 2007)

"Overall mammographic density seems to represent a general marker of breast cancer risk that is not specific to breast side or location of the eventual cancer."

Lifetime physical activity and the risk of breast cancer: A case-control study. (Cancer Detect Prev. 2007)

"Conclusions: These data are in concordance with the hypothesis that lifetime total physical activity is associated with decreased breast cancer risk. They also suggest that recreational physical activity at ages 14-20 years is the most beneficial. In addition, these findings confirm the majority of previous reports which implicated physical inactivity as important risk factor for breast cancer."

Highlighted Internet Site

NCI - Breast Cancer (PDQ®): Prevention