Isolated mediastinal lymphangioma herniating through the intercostal space.

Lymphangiomas are congenital malformations of the lymphatic system, and 90% have manifested by the end of the second year of life. While 75% of these are located in the cervical region, only 2% to 3% are associated with an intrathoracic extension. An isolated mediastinal lymphangioma without a cervical component is an uncommon occurrence.