Primary orbital rhabdomyosarcoma in an adult.

PURPOSE. Rhabdomyosarcoma is the most common primary orbital malignant tumor in children. Though rare above the age of twenty, the authors present a case of primary orbital rhabdomyosarcoma in an adult and review the literature. DESIGN. Clinico-pathologic case report. METHODS. A 34-year-old man presented with a recurrent orbital tumor four years after initial excision. This tumor was initially misdiagnosed elsewhere as Merkel cell tumor on the basis of spurious immunohistochemical studies. Excision biopsy of the recurrent orbital mass was performed. MAIN OUTCOME MEASURES. MRI of the orbit and brain was done as well as histopathologic examination and immunohistochemistry of the excised mass. RESULTS. Histopathologic study of the excised orbital tumor revealed rhabdomyosarcoma. CONCLUSION. Careful microscopic evaluation and immunohistochemical stains are important in confirming the diagnosis of atypical cases of orbital tumors.