Most commonly both breasts are normal shape but simply different sizes. This is true developmental breast asymmetry. Another common pattern in this group is one small conical (pert) breast and another larger breast but with droop. Both in themselves are acceptable shapes but different in the same patient.
The next group have abnormal breast shape. The breast is often very constricted with a very narrow base but a small droopy breast and large nipple. This is the tuberous breast deformities.
The third group of patients are associated with absence of underlying muscles and sometimes rib-cage and is called Polands Syndrome.