What is Breast Cancer?
Breast cancer is the most common cancer in American women, and it is the second most common cause of cancer deaths in women. (Lung cancer still kills almost 4 times as many women each year as breast cancer.) Breast cancer occurs rarely in men as well. There are about 230,000 new cases of breast cancer diagnosed in women the U.S. each year, and about 2,300 new cases diagnosed in men.
To understand breast cancer, it's important to learn the anatomy of the breast. Most of the breast is comprised of fatty (adipose) tissue, and within that are ligaments, connective tissue, lymph vessels and nodes, and blood vessels. In a female breast there are 12-20 sections within it called lobes, each made up of smaller lobules that produce milk. The lobes and lobules are connected by ducts, which carry the milk to the nipple.
The most common type of breast cancer is cancer of the ducts, called ductal carcinoma that accounts for just over 80% of all breast cancers. Cancer of the lobes (lobular carcinoma) makes up just over 10% of cases. The rest of the breast cancers have characteristics of both ductal and lobular carcinomas, or have unknown origins.