You are correct that sometimes large differences in breast size is considered a condition called Breast Asymmetry. Sometimes these differences can result in back pain, neck pain, difficulty with clothing choices and daily activities such as exercise. Although you are young, it would be reasonable to see a Board Certified Plastic Surgeon with your parents to be evaluated for a possible future procedure to correct the asymmetry. In order to make the breasts more even, sometimes the smaller breast is enlarged with an implant or the larger breast is reduced with surgery. Sometimes both of these procedures are required and even sometimes a lifting procedure is performed if one side droops more than the other. The timing of the surgery will depend on your growth status and whether you and your parents feel you are ready. The good news is most of the time the symmetry is improved enough that you can look even in clothing and bathing suits. Patients who have these procedures are typically very satisfied