[Posterior mediastinal thymus. Apropos of a case in a child].

Posterior and upper mediastinal localization of the thymus gland is uncommon in young children. Presenting symptoms and signs are very variable from incidental diagnosis to bronchopneumonial with atelectasias of the left upper Chest X-Ray and CT Scan are sufficient to make the diagnosis. Treatment of complicated forms with bronchial compression requires thoracotomy and surgical excision.