A case of sinus histiocytosis with massive lymphadenopathy is reported. A Japanese woman noticed gingival swelling when she was 27 years old. One year later, nasal obstruction and swelling of right cervical lymph node developed. Lymph node biopsy showed pericapsular fibrosis, dilatation of sinus, plasma cell infiltration in medullary cords, and marked increase in large histiocytes in sinuses and paracortical areas. Enlarged histiocytes were S-100 protein-positive and muramidase-negative, and engulfed not only lymphocytes but also plasma cells, neutrophils, and muramidase-positive monocytes. Laboratory data showed lymphocytopenia, hypergammaglobulinemia, and elevated erythrocyte sedimentation rate. She was treated with antibiotics, prednisolone, OK432, and irradiation without beneficial effects. Although sinus histiocytosis with massive lymphadenopathy involved cervical, axillary, and inguinal lymph nodes and nasal cavity in this patient, her symptoms and signs subsided spontaneously after 89 months from the onset of lymphadenopathy.
