Hi - First of all, your great aunt having had breast cancer doesn't increase your risk, so you can put that thought aside. Second, at your age, breast cancer is extremely, EXTREMELY unlikely. If your nipple has just started to be inverted; and if your left breast has just recently grown larger than the right; and if this lump is new, then you should get checked out. It's more than likely you have something called fibrocystic change, which is very common in women your age; but if these are all new symptoms, then they qualify as breast change, and you should see a doctor, OK? Good luck - PJH