Isolated costal cartilage fracture: an unusual cause of an anterior chest mass in a toddler.

A 17-month-old boy presented with a palpable anterior chest wall mass and was evaluated by chest radiography, sonography, and MRI. No history of trauma was provided initially. Sonography and MRI showed a costal cartilage fracture with overlying hematoma. Identification of a fracture isolated to the costal cartilage is rare and this is a unique case among children. In the appropriate clinical setting, costal cartilage fractures can be confirmed by sonography alone, and follow-up assessment can be based on clinical evaluation without the need for additional cross-sectional imaging.