Generally, Cancer is the result of cell mutations, or abnormal changes in the growth of regular cells and this behaviour of cells become out of control.
Breast cancer refers to a kind of cancer, a malignant tumor (a group of cancer cells) which develops in the cells of the breast, usually in the ducts or lobules area of the breast.
A breast cancer that develops in the ducts is called ductal carcinoma and while it develops in the lobules is known as lobular carcinoma.
This cancer occurs almost entirely in women, but men can get it, too.