Extraventricular neurocytoma with atypical features and ganglionic differentiation.

Extraventricular neurocytoma (EVN) is an unusual variant of central neurocytoma located outside the ventricular system. Both tumours share a similar histology characterised by monotonous populations of round-to-oval cells with scanty cytoplasm separated by neuropil and branching capillaries. We report an EVN arising from the right frontal lobe near the olfactory tract in a 34-year-old male with worsening chronic epilepsy. Our patient's tumour exhibited many uncommon features including ganglionic differentiation, increased mitotic activity and a high proliferative index. We discuss the important differential diagnoses given the site of the tumour as well as the differentiating features from olfactory neuroblastoma, oligodendroglioma, anaplastic ganglioglioma and supra-tentorial primitive neuroectodermal tumour.