Extraskeletal mesenchymal chondrosarcoma of the orbit.

Mesenchymal chondrosarcoma, an uncommon lesion of bone and extraskeletal tissue, is rare in the orbit. A case of extraskeletal mesenchymal chondrosarcoma of the orbit in a 28-year-old woman presenting with proptosis and diminution of vision in the left eye is reported. Histologically, the tumor showed areas of undifferentiated mesenchymal cells with islands of cartilage. Immunohistochemical analysis for S-100 protein showed focal positivity in chondroid areas. The eye was preserved and the patient has good vision after 2 years of follow-up.