Brittany, most breast lumps are not cancer and that is especially true for young women. Sometimes breasts are especially lumpy before a menstrual period. You don't need to panic about this; however, you do need to tell your parent or guardian about what you found. If the lump lasts longer than a menstrual period, you need to show it to a doctor. The most common breast lump in teenagers is called a fibroadenoma, and it is not dangerous. Sometimes a lump is actually an abcess (infection), and while it is not cancer, it does need prompt medical treatment. Only a doctor can tell one kind of lump from another.