Diffuse leptomeningeal glioneuronal tumor in an 8-year-old girl: case report and review of the literature.

Diffuse leptomeningeal glioneuronal tumors (DLGNTs) are rare central nervous system tumors of childhood that were recently described as a new entity. DLGNTs usually manifest with symptoms related to increased intracranial pressure or spinal cord compression. The classic radiological feature is a widespread leptomeningeal enhancement that may involve the entire neuroaxis. Microscopic examination demonstrates oligodendroglial-like cells that are positive for OLIG2, MAP2, and S100 and negative for IDH-1. Anaplastic features occur in some cases. Molecularly, DLGNTs are characterized by chromosome arm 1p deletion and alteration of a mitogen-activated protein kinase (MAPK) pathway gene, most commonly BRAF-KIAA1549 fusion. There is no established grading system for these tumors, which may have an indolent or aggressive behavior. Treatment usually involves chemotherapy and radiation therapy.