This document discusses breast masses in children and adolescents. The majority of breast masses in these groups are benign and self-limited. Common benign causes include breast hypertrophy in neonates, breast buds in pubertal children, fibrocystic disease, and fibroadenomas in adolescents. Rarely, breast cancer can occur. Evaluation involves history, examination, and possibly ultrasound or biopsy. Treatment depends on diagnosis but most benign masses require only observation.