[Cystic lymphangioma of the mediastinum. Apropos of 3 cases, review of the literature].

Cystic hygromas are benign cysts frequently discovered incidentally on chest X ray films. Although CT scan provides helpful information about the size, density, and site of the cysts, it cannot establish a precise diagnosis concerning its nature. Complete removal of the cyst is the treatment of choice, and allows precise diagnosis on histological examination. However, surgical excision is sometimes difficult, due to the size and extension of the cysts, infiltrating mediastinal planes, enveloping great vessels, displacing mediastinal organs without invasion. The difficulty of completely eradicating certain cysts explains cases of insidious progression with compressive recurrence.