A rare diagnosis of an extraventricular neurocytoma

Abstract

Background: Extraventricular neurocytoma (EVN) is an extremely rare neoplasm of the central nervous system. As reported, it arises in a variety of locations, but mainly within the cerebral hemispheres. Despite its histological similarity with central neurocytoma (CN), EVN occurs outside the ventricular system and, in 2007, was recognized by the World Health Organization as a separate entity.

Case description: A 39-year-old man, with a ventriculoperitoneal shunt inserted for communicating hydrocephalus, was admitted at our Unit of Neurosurgery with a 1-month history of gait disturbance, postural instability, speech disorders, and occasional incontinence. Computed tomography scan and magnetic resonance imaging showed a mixed-density neoplasm in the left frontotemporal area, with anterior cerebral falx shift, and perilesional edema. The patient underwent surgical procedure; microsurgical excision of the lesion was performed through left pterional approach. Histopathological and immunohistochemical examination revealed monomorphic round cells of the neuronal lineage, with a percentage of Ki-67 positive nuclei <5% and no evidence of mitosis or necrotic areas. According to radiologic features, this pattern was compatible with the diagnosis of EVN. Patient had a favorable recovery and he is still in follow-up.

Conclusion: Because of their rarity, clinical, radiologic, and histopathological characteristics of EVNs are not yet well defined, as well as the optimal therapeutic management. Whereas EVNs are rarely described in literature, we aimed to share and discuss our experience along with a review of the published literature.

Keywords: Extraventricular neurocytoma; Neurocytoma; Neuronal tumors.

Figure 1:

Preoperative contrast brain computed tomography scan showing the left frontotemporal non-homogeneous neoformation, with several calcifications, hypodense colliquated areas, and perilesional edema.

Figure 2:

Preoperative contrast brain magnetic resonance imaging, showing the lesion with lobulated margins, non-homogeneous post contrast enhancement, solid component mixed with necroticcolliquative areas and calcifications. (a) axial plane, (b) sagittal plane, (c) coronal plane.

Figure 3:

(a) On low power histopathological examination, sheets of monomorphic round cells interspersed by fine capillary channels and laminated concentric microcalcification, without evidence of ischemic necrosis or hemorrhage. (hematoxylin and eosin [H and E] ×40), (b) Higher magnification shows round cells with stippled chromatin arranged in a background of finely fibrillar neuropil cores (hematoxylin and eosin [H and E] ×250), (c) strong immunoreaction for synaptophysin expressed by tumor cells (avidin-biotin ×250).

Figure 4:

Postoperative brain computed tomography scan.

Figure 5:

Postoperative brain magnetic resonance imaging showing large area of structural alteration, consisting predominantly of cerebrospinal fluid and a tissue portion with calcifications. (a) axial plane, (b) sagittal plane, (c) coronal plane.