Primary disseminated leptomeningeal oligodendroglioma with 1p deletion. Case report.

The authors report the case of a 2-year-old boy with a primary, diffuse leptomeningeal oligodendroglioma in which the deletion of chromosome arm lp was identified by performing a fluorescence in situ hybridization (FISH) analysis. This previously healthy child initially presented with malaise, anorexia, nausea, vomiting, and macrocephaly. Imaging studies confirmed the presence of hydrocephalus, and a ventriculoperitoneal shunt was placed. The postoperative course was complicated by emesis, continued weight loss, and numerous seizurelike episodes. A contrast-enhanced magnetic resonance imaging study performed approximately 10 weeks postoperatively showed diffuse leptomeningeal thickening and enhancement without evidence of an intraparenchymal mass lesion. A right frontal lobe brain biopsy revealed a hypercellular proliferation of small oligodendroglioma-like cells, which occupied the leptomeninges diffusely and spared the underlying cortical gray matter. The tumor cells displayed prominent perinuclear clearing and had evenly spaced, uniformly round nuclei. Occasional mitotic figures were observed. Background vessels were thin and delicate, and there was no evidence of necrosis. The tumor cells showed strong immunoreactivity for S100 protein; the results of immunohistochemical staining were negative for glial fibrillary acidic protein, vimentin, epithelial membrane antigen, NeuN, and synaptophysin. The deletion of lp was demonstrated by FISH analysis; lq, 19p, and 19q were intact. This appears to be the first reported case of a primary diffuse leptomeningeal oligodendroglioma in which a lp deletion was identified.