Causes

Recurrent breast cancer occurs when cells that were part of your original breast cancer break away from the original tumor and hide nearby in the breast or in another part of your body. Later, these cells begin growing again.

The chemotherapy, radiation, hormone therapy or other treatment you may have received after your first breast cancer diagnosis was intended to kill any cancer cells that may have remained after surgery. But sometimes these treatments aren't able to kill all of the cancer cells.

Sometimes cancer cells may be dormant for years without causing harm. Then something happens that activates the cells, so they grow and spread to other parts of the body. It's not clear why this occurs.