Orbital granular cell tumor in a patient with Churg Strauss syndrome: the importance of biopsy.

A 65-year-old woman presented with a long standing, progressive exophthalmos of the right eye. Her medical history was significant for Churg Strauss syndrome, and was treated with immunosuppressive therapy. She had undergone two previous orbital biopsies showing inflammatory reactive lymphoid hyperplasia. A diagnosis of orbital inflammation in Churg-Strauss syndrome was suspected, and the immunosuppressive therapy was increased. Because of the lack of response to therapy, a further biopsy was performed, by lateral orbitotomy approach. Biopsy of the mass revealed a granular cell tumor composed of S-100 positive cells with an acidophilic granular cytoplasm and peripheral lymphocytic infiltration. A granular cell tumor, which is very rare in the orbit, should be considered in the differential diagnosis of orbital tumors, and if suspected, an excisional biopsy must be undertaken. Typical histopathological aspect of the granular cell tumor is characterized by the presence of S-100 positive closely packed polygonal cells with a granular cytoplasm.