Primary leptomeningeal histiocytic lymphoma in a young child.

A 20-month-old boy had an 8-week history of vomiting, lethargy, generalized muscle weakness, and seizures. There was no history or clinical signs of an underlying systemic disease or an immunodeficiency. Cerebrospinal fluid (CSF) had 99 nucleated cells/cu mm, malignant cells, high protein and normal glucose. CT and MRI scans showed diffuse meningeal enhancement around the brain and spinal cord, but no parenchymal involvement. Biopsy of the leptomeninges showed malignant cells with marked nuclear pleomorphism and prominent clear to eosinophilic cytoplasm. The immunohistochemical studies were positive for histiocyte-macrophage markers and were negative with T and B cells, Ki-1, neural and glial cell antibodies. Multiple tests revealed no other site of disease. The patient died 3 months after onset of treatment despite intensive i.v. and intrathecal chemotherapy. We have not found any other reported case of primary histiocytic leptomeningeal lymphoma in a young child.