Sonographic features of physiologic neonatal breast enlargement

The varying presentations of neonatal breast enlargement on imaging have been underreported in the literature. Our case report profiles a 3-week-old female patient who presented with a history of left breast enlargement with redness and tenderness for 2 days, who was clinically diagnosed and managed for neonatal mastitis, which was actually a neonatal breast enlargement with adjacent cellulitis. Awareness that physiologic neonatal breast enlargement can be associated with adjacent cellulitis without mastitis can prevent unnecessary hospitalization and treatment with parenteral antibiotics.