Atypical extraventricular neurocytoma

Abstract

The authors report a case of atypical extraventricular neurocytoma (EVN) transformed from EVN which had been initially diagnosed as an oligodendroglioma 15 years ago. An 8-year-old boy underwent a surgical resection for a right frontal mass which was initially diagnosed as oligodendroglioma. When the tumor recurred 15 years later, a secondary operation was performed, followed by salvage gamma knife treatment. The recurrent tumor was diagnosed as an atypical EVN. The initial specimen was reviewed and immunohistochemistry revealed a strong positivity for synaptophysin. The diagnosis of the initial tumor was revised as an EVN. The patient maintained a stable disease state for 15 years after the first operation, and was followed up for one year without any complications or disease progression after the second operation. We diagnosed an atypical extraventricular neurocytoma transformed from EVN which had been initially diagnosed as an oligodendroglioma 15 years earlier. We emphasize that EVN should be included in the differential diagnosis of oligodendroglioma.

Keywords: Atypical extraventricular neurocytoma; Differential diagnosis; Oligodendroglioma; Recurrence.

Fig. 1

A : Preoperative T2-weighted image from the surgical specimen at the first operation demonstrates heterogeneous signal intensity in a right frontal mass. B : Contrast-enhanced T1-weighted image shows subtle peripheral enhancement 13 years after the first operation. C : T2-weighted image taken 15 years after the first operation demonstrates high signal intensity mass lesion in the right frontal lobe. D : Contrast-enhanced T1-weighted image taken 15 years after the first operation shows marked enhancement. E : 18F-FDG brain positron emission tomography shows a hypermetabolic lesion in the right inferior frontal lobe.

Fig. 2

A : H&E staining shows round to oval, small uniform cells from the specimen taken at the first operation (Magnification; ×200, H&E stain). B : Immunostaining for synaptophysin demonstrates a strong positivity in the specimen taken at the first operation (Magnification; ×400, synaptophysin immunochemical stain). C : Small round cells with large clear cytoplasms and round nuclei (Magnification; ×400, H&E stain). D : A strong positivity for synaptophysin is seen (Magnification; ×400, synaptophysin immunochemical stain). E : Electron microscope shows that the cytoplasmic organelles are sparse and include a few strands of RER cisternae, dense bodies and glycogen particles (Magnification; ×7,000, electron microscopy).