Diffuse leptomeningeal glioneuronal tumors: a new entity?

Abstract

The peculiar radiological and pathological findings of four pediatric cases admitted to the University Hospital of Padua between 1990 and 2007 are described. In all cases, the contrast-enhanced head and spine magnetic resonance images revealed thickened and abnormally enhancing subarachnoid spaces particularly at the level of basal cisterns and interhemispheric fissure. Furthermore, small cystic lesions scattered throughout the brain and mainly in the cerebellum were also visible. All patients were missing a well-defined intraparenchymal mass, although during the follow-up a small intramedullary lesion appeared within the cervical spine in two and subsequently in the frontal horn of the left lateral ventricle in one of those. All patients presented an indolent long-term follow-up. Histologically, the tumors were composed by a monotonous population of cells arranged in straight lines or in small lobules. The cells were characterized by round to oval nuclei with finely granular dispersed chromatin, inconspicuous nucleoli with oligodendrocyte-like features. The morphological and immunohistochemical findings suggested in all cases a "glioneuronal commitment" of the tumors. Because of the unique similar clinical and neuroradiological characteristics, we propose this small series of tumors as a new possible distinct pathological and clinical entity.

Figure 1

Representative neuroradiological features of the described tumors at initial presentation. A,B. Axial T2 images show cystic lesions diffusely scattered throughout the surface of the cerebellum, brain stem, mesial temporal lobes and basal frontal lobes. C. Axial and D. coronal contrast‐enhanced T1 images demonstrate thickening and enhancement of the leptomeninges. A tetraventricular communicating hydrocephalus is also present. E. Spinal sagittal T2 image reveals small cystic lesions involving the posterior surface of the conus midollaris (black arrows). F. Corresponding contrast‐enhanced T1 image demonstrates a marked nodular and linear leptomeningeal enhancement involving the spinal cord and the cauda equina; the intra‐axial cysts do not enhance. Spinal axial. G. T2 and H. contrast‐enhanced T1 images at cervical level show a small superficial leptomeningeal enhancing nodule (white arrow) and an underlying intramedullary cyst (open arrow). I. Sagittal contrast‐enhanced T1 images depict a small intramedullary lesion posterior to C3‐C4 (white arrow) and a marked cerebral and spinal leptomeningeal enhancement coexisting with a tetraventricular communicating hydrocephalus and an empty sella. Small non‐enhancing cysts are scattered throughout the cerebellar and pontine surface. (A,C,D–H case #1; B and I, case #3).

Figure 2

Representative histopathological features of the described tumors. A. Thickened leptomeninges diffusely infiltrated by neoplastic cells. B. Tumors were composed by a monotonous population of round cells arranged in straight lines. C. Pseudopapillary pattern of neoplastic growth. D. Cuboidal glial cells intermingled with neurocytes and ganglioid cells. E. Intratumoral neural pseudorosettes were also observed. F. Oligodendrocyte‐like honeycomb appearance. G. Strongly cytoplasmatic synaptophysin‐immunoreactive tumor cells. H. Nuclear Neu‐N‐immunoreactive neurocytic component. Original magnifications 10×, 20× and 40×. (A, case #1; B, case #4; C–H, case #3).