MALIGNANT RHABDOID TUMOR OF THE ORBIT

A 36-month-old girl had a 3-week history of proptosis of the right eye . Computed tomography showed an ill-defined homogeneous mass filling t he intraconal space. Histopathologic examination and immunohistochemis try findings of an incisional biopsy specimen were consistent with mal ignant undifferentiated tumor with rhabdoid features. Despite chemothe rapy (a combination of vincristine sulfate and dactinomycin) and radio therapy, massive orbital recurrence occurred 6 months later and orbita l exenteration was performed, The recurrent tumor was composed entirel y of pleomorphic epithelial cells with prominent nucleoli and many fil amentous cytoplasmic inclusions, Immunohistochemical staining showed p ositive immunoreactivity for vimentin, cytokeratin, and epithelial mem brane antigen, and negative immunoreactivity for muscle-specific antig en, melanoma, neural, and histiocytic markers. Electron microscopy exc luded myogenic differentiation and showed that the filamentous cytopla smic inclusions were composed of whorls of intermediate filaments. Agg ressive chemotherapy with a combination of vincristine, doxorubicin, c yclophosphamide, ifosfamide, and etoposide phosphate was continued aft er exenteration, At 17 months' follow-up, orbital debulking surgery wi th externalization of the maxillary sinus was performed because of mas sive tumor recurrence in the right orbit and growth into the maxillary sinus, The child died 23 months after initial diagnosis from tumor in vasion into the central nervous system, Extrarenal rhabdoid tumor is a rare orbital mass that carries a poor prognosis.