A clinicopathologic study of extraventricular neurocytoma

Abstract

In 2007, extraventricular neurocytoma was classified as a separate entity among glioneuronal tumors. However, extraventricular neurocytoma is not fully understood and may be misdiagnosed. Here, we describe the clinical and pathological features, prognoses, and treatments of 13 extraventricular neurocytoma cases, and compare their immunophenotypes with those of oligodendroglioma, diffuse astrocytoma, and ependymoma. Six typical and 7 atypical cases comprised the 13 extraventricular neurocytoma cases. Histological features included oligodendroglioma-like perinuclear halo, neuropil-like matrix, ganglion or ganglioid cells, perivascular pseudorosettes, vessel hyalinization, calcifications, and myxoid degeneration. Atypical histological features included increased mitotic figures, focal necrosis, endothelial cell proliferation, and/or a Ki-67 index of >2%. All lesions expressed synaptophysin and microtubule-associated protein-2, which distinguished them from other similar tumors. Two patients with atypical extraventricular neurocytoma had tumor recurrence, one of whom had cerebrospinal fluid dissemination, suggesting that atypical histological features might represent adverse prognostic factors. In conclusion, the present study identified morphological and immunohistochemical features that would aid the differential diagnosis of extraventricular neurocytoma. In addition, radiotherapy with subtotal resection could be considered an effective treatment for extraventricular neurocytoma, but because a pediatric patient died of intracranial hemorrhage during radiotherapy, radiotherapy-related side effects should be considered, especially when treating children. Additional cases with long-term follow-up are needed to develop optimal management protocols for extraventricular neurocytoma.

Malignant progression of an extraventricular neurocytoma arising from the VIIIth cranial nerve: A case report and literature review

“…Neurocytoma can also occur in brain parenchyma, or even in sites remote from the ventricles. Therefore, the latter tumor was named EVN . Histopathologically, both CN and EVN display uniform, small, round cells with clear cell cytoplasm in a neuropil background .…”

“…However, EVN shows a wide variety of histology compared with CN. EVNs can exhibit sheet‐like structures, Homer‐Wright rosettes, and ganglionic differentiation, unlike CN . In addition, EVNs can exhibit hyalinized vessels and myxoid stroma, but CN rarely does so .…”

“…In adults, EVNs are most likely to occur within the frontal lobe, followed subsequently by the temporal lobe, parietal lobe and occipital lobe . In addition, exophytic neurocytomas of the thoracic spinal cord have been reported . However, EVN involving a cranial nerve is extremely rare.…”

“…CN is a low‐grade neoplasm that is characterized by its intraventricular localization, its occurrence predominantly in young adults, its histological resemblance to oligodendrogliomas, and its expression of neuronal markers . Shortly after the establishment of CN, similar tumors of the central nervous system were reported in several locations outside the supraventricular system as extraventricular neurocytomas (EVNs) . Histologically, EVN is an unusual tumor that is histologically composed of small uniform cells that demonstrate neuronal differentiation.…”

“…[1][2][3][4][5] Shortly after the establishment of CN, similar tumors of the central nervous system were reported in several locations outside the supraventricular system as extraventricular neurocytomas (EVNs). [6][7][8][9][10][11][12][13][14] Histologically, EVN is an unusual tumor that is histologically composed of small uniform cells that demonstrate neuronal differentiation. EVNs also display a histological resemblance to oligodendrogliomas.…”