Embryonal rhabdomyosarcoma of the orbit in a 35-year-old man.

A 35-year-old man had rapidly progressive proptosis of the right eye with associated chemosis over a period of several weeks. Computed tomography demonstrated a solid extraconal mass in the inferior anterior right orbit. Pathologic examination revealed the lesion to be an embryonal rhabdomyosarcoma. Consistent with the diagnosis, immunohistochemical assays demonstrated positive staining with myoglobin, desmin, and muscle-specific actin. The lesion grew rapidly and was further surgically excised. Subsequently, treatment with radiation and chemotherapy was initiated. Primary embryonal rhabdomyosarcoma of the orbit is an extremely rare tumor in adults, and, to our knowledge, this patient represents the oldest individual reported to have developed such a tumor, as documented by immunohistochemical analysis.