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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.

Striking similarities between the pineals of 107 fetuses and infants and a pigmented neuroectodermal tumor occurring in the right orbital and right frontal regions in a 6-month-old Puerto Rican boy were found. Both the human fetal pineal and melanotic neuroectodermal tumors of infancy are characterized by pigmented (melanin) epithelial cells, small undifferentiated cells, and a fibrovascular stroma. Our findings suggest the fetal pineal may be a normally occurring precursor of the melanotic neuroectodermal tumor of infancy, or that melanin production may be a normal capability of differentiating neuroepithelial cells.