Mediastinal lymphangioma.

Mediastinal lymphangioma is an uncommon benign tumor accounting for 0.7 to 4.5% of all mediastinal masses. Lymphangiomas consist of dilated cystic lymph spaces lined by single layers of endothelium and do not undergo malignant change. Most mediastinal lymphangiomas are asymptomatic. There are no specific radiological findings. Surgical excision is the treatment of choice and the prognosis is excellent.