A 10-YEAR-OLD Iraqi child presented with a bilateral exophthalmos (Figure 1). An ophthalmologist had partially stitched up his eyelids to avoid subluxation of the globes. Exophthalmos began at age 3 years and was diagnosed as pseudotumor orbitae. Attempted control of progressive proptosis with steroid therapy had been unsuccessful. Health status was otherwise normal. Erythrocyte sedimentation rate and serum immunoglobulin levels were elevated. A cranial magnetic resonance imaging scan showed abnormal tissue completely occupying the orbital spaces (Figure 2), the sphenoidal and maxillar sinuses, the right retrostyloid space, and slightly infiltrating the anterior fossa up to the sella. Chest x-ray films, radionucleotide bone scan, and bone marrow aspirate showed no abnormalities. An orbital tissue biopsy specimen showed sheets of large, pale, eosinophilic polygonal histiocytic cells with large vesicular nuclei and small nucleoli; occasional multinucleated histiocytes and spindle-shaped histiocytes were also present. No intact lymphoid cells were detected in the cytoplasm of large histiocytes (ie, no emperipolesis), mitosis was rare, and small lymphocytes and plasma cells were frequently scattered throught the lesion as single cells and also arranged in clusters (Figure 3, left). By immunohistochemistry the histiocytic cells stained positive for S100 protein (Figure 3, right) and CD68, but negative for CD1a (not shown); a presumptive diagnosis of Rosai-Dorfman disease of soft tissue was made. Diagnosis of multifocal Rosai-Dorfman disease of the soft tissue was then confirmed with a biopsy specimen of an asymptomatic, mildly enlarged submaxillar lymph node. At histological examination, the lymph node architecture was preserved and the sinuses were distended by distinctive large histiocytes with abundant pale cytoplasm, often filled with apparently intact lymphocytes (emperipolesis). By immunohistochemistry the histiocytic cells stained positive for S100 protein and CD68, but negative for CD1a (not shown). These cells showed the same phenotype observed in orbital tissue (Figure 3). Sixteen weeks of chemotherapy (vinblastine, 6 mg/m2 per week), gave poor results. Further chemotherapy with mercaptopurine (60 mg/m2 per day) and methotrexate (12 mg/m2 per week) for another 16 weeks also gave poor results.