Extranodal sinus histiocytosis with massive lymphadenopathy presenting as an intramedullary spinal cord tumor: a case report.

Involvement of the central nervous system by sinus histiocytosis with massive lymphadenopathy (SHML) is rare. Less than 30 cases have been reported. To the best of our knowledge, we describe the first case of an intramedullary spinal cord lesion which occurred in a 34-year-old black male, causing paraplegia. Laboratory evaluation revealed anemia, increased erythrocyte sedimentation rate, and polyclonal gammopathy. Microscopic examination of the lesion revealed lymphocytes within the cytoplasm of the histiocytic cells, a phenomenon known as emperipolesis. Immunohistochemical stains showed the large eosinophilic histiocytic cells to be positive for S-100 protein and Kp1 antigen. Special stains for fungi and acid-fast organisms were negative. There was no evidence of clonality in the lymphocytic aggregates. Glial fibrillary acidic protein was negative in the lesion, although positive in the surrounding tissue. These features confirmed the diagnosis of extranodal SHML involving the intramedullary spinal cord.