Mesenchymal chondrosarcoma of the orbit masquerading as a hemophilic pseudotumor.

An 11-year-old boy presented with a lesion of the right orbit that was thought to be a hemophilic pseudotumor. Excisional biopsy revealed an unexpected diagnosis of mesenchymal chondrosarcoma. Both mesenchymal chondrosarcoma and hemophilic pseudotumor of the orbit are exceedingly rare. To the best of our knowledge, this is the first reported case of orbital mesenchymal chondrosarcoma masquerading as hemophilic pseudotumor.