A lymphangioma (congenital malformation consisting of focal proliferations of well-differentiated lymphatic tissue in multi cystic or sponge like structures) located within the mediastinum, i.e., the central compartment of the thoracic cavity that is surrounded by loose connective tissue. Mediastinal lymphangioma is a slow growing mass with benign features, and accounts for 1% of all mediastinal tumors.