Snowstorm appearance on breast ultrasound is associated with which structure?

• A. Lactiferous ducts
• B. Cooper's ligaments
• C. Pectoralis muscle
• D. Rib and chest wall muscle

Answer: (A)

Snowstorm appearance on breast ultrasound comes from dense, finely scattered echoes inside milk-containing structures, typically a dilated lactiferous duct or galactocele in lactating breasts. When a duct becomes obstructed and milk is inspissated, debris and milk crystals create numerous small reflecting particles that scatter the ultrasound beam, producing a speckled, snow-like pattern. This intraductal debris is the hallmark sign, distinguishing it from patterns seen in other tissues. Cooper’s ligaments would show linear echogenic bands, pectoralis muscle has a fibromuscular pattern, and rib/chest wall structures would show bone with overlying soft tissue—none of which generate the characteristic diffusely speckled snowstorm appearance. The snowstorm sign in ducts reflects the presence of milky debris within the ductal system rather than surrounding muscles or ligaments.