Breast cancer starts in the breast tissue, starts growing uncontrollably, and usually becomes a solid tumor. In the United States, it is the second most common type of cancer in women and it only rarely occurs in men. Most often, breast cancer starts in the ducts, which are the tubes that carry breast milk to the nipple.[1]
What is breast cancer?
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•Last Updated: May 16, 2025
Breast cancer begins in the breast tissue, grows uncontrollably, and typically forms a solid tumor. It is the second most common cancer among women in the U.S. and primarily originates in the milk-carrying ducts.