Breast cancer is when there are bad cells that grow in a woman's breast. Every woman has two of them, and they usually make milk to feed a baby. But sometimes, the cells start to grow too much and become a lump.
Some lumps are good and some are bad. Doctors can only tell which kind it is by checking it. They may use special pictures like x-ray to see inside the breast.
If the lump is bad, it means there are bad cells growing there. They can spread to other parts of the body and make someone feel sick. That's why it's important to find out early and take medicine to make it better.
To prevent breast cancer, a woman can check her breasts every month by herself or with help from her mom or dad. Doctors also can check them every year to make sure everything is okay.