Hi - at age 16, your chances of having breast cancer are practically non-existent. It's good you're aware of breast changes; but at this point, probably nothing to worry about. I'd keep track of the lump you feel in your left breast, and if it's hard, doesn't move around, and doesn't change, I'd bring it up with your doctor, OK? Just to be absolutely sure and set your mind at ease. Good luck - PJH