GAMUT I-18
ASYMMETRY OF PECTORALIS MUSCLE ON MAMMOGRAPHY (usually on MLO view)


COMMON
1. Inadequate or improper positioning
2. Muscular dystrophy
3. Normal variant
4. Prior surgery injuring pectoralis with atrophy (eg, multiple difficult implant placements and removals with or without silicone extravasation)
5. Stroke
6. Trauma (esp. in childhood) 


UNCOMMON
1. Poland syndrome (pectoral muscle aplasia-syndactyly)
2. Poliomyelitis





References