ABSTRACT
Primary extraskeletal osteosarcoma (EOS) is an extremely rare malignancy. In this report, the clinical course of a 32-yearold man presenting with proptoses is described. Medical history included Hirschsprung disease (HD), horseshoe kidney, azoospermia, and vertebral anomalies. Imaging of the orbit showed an oval, well-defined heterogeneous mass adjacent to the lateral wall of the orbit. The patient underwent a lateral orbitotomy and complete excision of the mass. The mass was not attached to the bone. Histopathologic and immunohistochemical examination confirmed the diagnosis of an EOS. The patient received chemotherapy and radiotherapy and is free of the disease 3 years after the diagnosis. Genetic screening showed no mutations for both the RET protooncogene for HD and the p53 tumor suppressor gene for osteosarcoma.