About one in every eight women develops breast cancer. When the cancer spreads, it can form new tumors in other parts of the body. These new tumors are called metastases. If the cancer spreads through the blood, it most commonly travels to the bones of the pelvis, spine, legs, ribs, and skull. Metastases may also be found in the liver, lungs, and brain.
Cancers are uncontrolled growths of abnormal cells.
It is not known why they occur. However, some women are more likely to get cancer than others. Using birth control pills and oral estrogen does not seem to increase the risk of breast cancer. The lump is often difficult to feel. Sometimes the skin over the lump may be dimpled or wrinkled.