Spontaneous multiseptated cystic pneumomediastinum in a term newborn.

Pneumomediastinum usually occurs after assisted ventilation. Spontaneous pneumomediastinum without preceding assisted ventilation, and presenting as a huge cystic mass in a term newborn infant has rarely been reported. We report a term baby who developed respiratory distress at 2 days of age. A huge cystic tumor of the thymus or a congenital mediastinal cystic tumor was initially suggested by chest radiography and computed tomography. Follow-up chest film revealed a "spinnaker sail sign" which is a typical radiographic presentation of pneumomediastinum.