Hi,
In most cases, breast lumps are not a sign of breast cancer especially at your young age..
Most likely this could be one of many benign lumps like for example a cyst or a Fibroadenoma .These kind of lumps are not cancerous and are commonly found in women in their late teens and early twenties.The cause of these benign lumps are due to hormonal fluctuations.
Breast cancer is indeed rare at your age,but anytime you feel a lump in your breast,you have to be aware that it is an abnormality and it's always wise to have it examined by your health care provider who will be able to decide what to do about it.
Don't be scared,most likely it's nothing to worry about,but please go see your doctor for a check up okay?
Take care ...