A Case of Fibrous Histiocytoma in Orbit

ABSTRACT

Fibrous histiocytoma is a slow-growing mesenchymal tumor that most commonly occurs in soft tissue and retroperitoneum, with an occasional occurrence in the orbit. This mesenchymal tumor should be included in the differential diagnosis of orbital mass in adults because this tumor is radioresistant and prone to recurrences and malignant potential if incompletely excised. So complete excision is the treatment of choice. A case report of a healthy 27-year-old woman with a gradually increasing, non tender superonasal mass and proptosis in the left orbit. She also developed diplopia. CT scan and MRI showed a well-marginated and encapsulated homo-geneous 2 x3 cmsized mass in the superonasal portion of the left orbit. The tumor was totally excised under the impression of carvenous hemangioma. In H-E stain, tumor cell revealed a marked cellularity, storiform arrangement of ovoid to spindle cells but there was little nuclear polymorphism, atypism and absent mitosis. Results of immunohistochemical study showed positive cytoplasmic immunoreactivity to alpha-1-ntitrypsin antibody but negative to S-100 protein, smooth muscle actin, Neuron specific enolase. Masson-Trichrome stain showed positive. The final diagnosis of a benign fibrous histiocytoma invading the orbit was confirmed by histopathological examination. There was no recurrence for more than 14 months after complete surgical excision. We present the above case with a brief review of literature.