[An anterior mediastinal mass of rare etiology].

Hydatid cyst of the mediastinum is very uncommon. The diagnosis, usually evident in endemic regions in the case of a typical clinical-radiological presentation, is rather more difficult in certain atypical forms. We report a case of a 19-year-old man who presented with a mass of tumour like appearance in the anterior mediastinum. The diagnosis of mediastinal hydatid cyst was established by transthoracic needle biopsy and endoscopic bronchial aspiration revealed hydatid membranous debris. The diagnosis was confirmed when the mediastinal cyst ruptured into a bronchus. Thoracotomy was carried out with an uneventful post-operative recovery. This observation illustrates the diagnostic difficulties when a mediastinal hydatid cyst presents the appearances of a tumour. This possibility must be included in the differential diagnosis of every mediastinal mass, particularly in endemic regions.