Background: Extraskeletal osteosarcoma is a malignant tumour composed of an osteoid and/or cartilaginous matrix; it arises in soft tissues without connection to the skeleton, and to our knowledge, this type of tumour is extremely rare.
Case presentation: The present study reports a 57-year-old man with primary orbital extraskeletal osteosarcoma who presented with a history of painful swelling in the left orbit that had occurred for 11 months. Imaging of the orbit showed an atypical, well-defined heterogeneous mass attached to the posterior globe of the left orbit. The patient underwent an anterior orbitotomy and complete excision of the tumour. The mass was originated from neither the globe nor the bony orbital wall but from the soft tissue. Histopathology demonstrated an extraskeletal osteosarcoma. After 13 months of follow-up, there was apparent recurrence of the tumour. The medical history showed no complaints of previous trauma or radiotherapy.
Conclusions: ESOS is a highly malignant tumour. Immunosuppression, trauma and adjuvant radiotherapy are possible predisposing factors in the development of this tumour. Prompt recognition and thorough treatment are essential for preventing orbital lesions and presence of metastasis from other organs.
Keywords: Extraskeletal osteosarcoma; Orbit; Osteosarcoma.