Abstract: Orbital mesenchymal chondrosarcoma is a relatively rare ocular neoplasm, and the male: female ratio is 1.1:1. It is unilateral and occurs mainly in young adults which HEY1-NCOA2 gene fusion can be detected by molecular genetics. In the early stage, ocular compression symptoms such as proptosis and diminution of vision are the main symptoms. In severe cases, it may invade adjacent structures or organs, but distant metastasis is very rare. Characteristic calcification on imaging is helpful to assist the preoperative diagnosis. Mesenchymal chondrosarcoma is difficult to differentiate in histopathology which is a small round-cell tumor with typical biphasic histology. Currently, this tumor is treated primarily with surgical resection, and the recurrence rate is high, postoperative radiotherapy may improve the patient's prognosis. (Int Rev Ophthalmol, 2023, 47: 175-180)

Key words: orbit, mesenchymal chondrosarcoma