Breast cancer is cancer that starts in the breast — usually beginning as a group of cells that grow out of control and form a tumor. Without treatment, the cancer can spread to the rest of the breast, beyond the breast to the lymph nodes and to other areas of the body.
Breast cancer almost always affects women, but in rare cases men may develop breast cancer, too.
Breast cancers can be categorized into several types depending on where in the breast the disease begins, how the cancer spreads and other factors. Some breast cancers are a combination of cancer types.
Breast cancer can be categorized as either invasive or noninvasive:
- Invasive breast cancer breaks through normal breast tissue barriers and travels to other parts of the body through the lymph nodes or blood.
- Noninvasive (in situ) breast cancer remains in the area of the breast where it started and does not spread.
The three most common types of breast cancer include:
Less common or rare types of breast cancer include: