[1509] Clinicopathological Study of Extraventricular Neurocytomas

JK Myung, B Kim, SJ Byun, SH Park. Seoul National University College of Medicine, Seoul, Republic of Korea

Background: From 1992, parenchymal counterpart of central neurocytoma (CN), extraventricular neurocytoma (EVN) started to be recognized, which share the histopathogical features of the CN but are known to show a wide morphological spectrum.
Design: Five recent cases of EVNs along with the clinicopathological and radiological findings are reviewed.
Results: The mean age of the patients was 36.2 years old (6 yrs66 yrs) and a female predominance (M:F=1:4) was found. The most common symptom was seizure (n=4) and the tumors were located in the temporal lobe (n=3), frontal lobe (n=1), and hippocampus (n=1). MRI showed nonenhancing cystic lesion (n=2), infiltrating solid mass (n=2), and well circumscribed mass with focal high signal intensity lesion on T2 and FLARE (n=1). Near total resection of the tumors were performed in every case. The tumor cells in all cases, regardless of the tumor grade, were composed of small round cells with round nuclei and clear or eosinophilic cytoplasm. These cells were arranged in sheet, in association with broad zone of fine neuropils. They superficially mimicked oligodendroglioma, but fried egg appearing cells were only focally observed. The cellularity was variable area by area. Often smaller ganglioid cells with nuclei that are larger and paler than neurocytes were detected. Three high grade ones showed high mitotic activity (7 to 9/10 HPF) and high level of MIB-1 labeling lndices (6 29 %). Two of them had vascular endothelial hyperplasia and necrosis. Almost tumor cells were immuno-labelled for synaptophysin and NeuN, and, additionally, expressed the nestin. GFAP expressing cells were observed focally, but pseudopapillary configuration was not shown. Ultrastructurally, neural tubules and synapses with synaptic junctions and synaptic vesicles were well observed. 1p/19q FISH study perfomed in 2 cases revealed no deletions. Radiotheraphy was offered to three patients with high grade ones. There were no case of recurrence in the course of follow-up periods (3 26 months) even though the follow up duration was not sufficiently long enough to confirm the biologic behavior.
Conclusions: EVNs were occurred in the patients with broad age ranges and epilepsy was most common symptom. Without immunohistochemistry, EVNs had a diagnostic pitfall due to spectrum of tumor cell morphology and similarity to oligodendrogliomas. More reports about its clinicopathological, biological and genetic studies are needed to understand and to have confidence upon this tumor.
Category: Neuropathology

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 202, Tuesday Morning