The breast is made up of specialized structures called ducts and lobules. Ducts are tiny tubes that carry milk to the nipple, and lobules are small glands that produce milk. These structures are lined with cells that normally grow and divide in a controlled and organized way.

Breast cancer begins when some of these cells develop changes that cause them to grow too quickly and ignore the body's normal signals to stop. Instead of forming healthy tissue, these abnormal cells begin to build up in one area.

At this early stage, the changes are happening on a very small scale, and there may be no noticeable symptoms. This is why early breast cancer is often difficult to detect without screening.