Benign sinus histiocytosis. Report of a case.

A case of benign sinus histiocytosis in a three-year-old girl is reported. She was evaluated for a six-month of significant enlargement of a lymph node at the side of the neck. The node was firm in consistency and nontender, with no inflammatory changes, but was responsible for venous compression and Horner's syndrome. Laboratory tests showed leukocytosis with predominance of neutrophils, elevation of the erythrocyte sedimentation rate, and hypergammaglobulinemia. The tuberculin skin test was negative and the chest film was normal. Histologic examination of the lymphadenopathy showed a histiocytic proliferation with plasma cells. There was no evidence of malignant disease. The outcome was favorable after surgery. Sinus histiocytosis is one of the reticulohistiocytoses, which are characterized clinically by involvement of multiple organs and tissues and histologically by a histiocytic proliferation. The cause is unknown. The outcome is favorable, either spontaneously or after surgical excision.