title: Radiological quiz.
abstract: The authors report a case of Letterer-Siwe syndrome presenting primarily as a mediastinal mass erroneously diagnosed as cystic thymoma. Although thymic involvement in Letterer-Siwe syndrome is common, only 2 previous cases have involved a mediastinal mass.
mesh_terms: D003937:Diagnosis, Differential; D005260:Female; D006646:Histiocytosis, Langerhans-Cell / Q000000981:diagnostic imaging*; D006801:Humans; D007223:Infant; D008479:Mediastinal Neoplasms / Q000000981:diagnostic imaging*; D011859:Radiography; D013945:Thymoma / Q000000981:diagnostic imaging*