Glioneuronal tumours with features of rosette-forming glioneuronal tumours of the fourth ventricle and dysembryoplastic neuroepithelial tumours: a report of three cases.

Aims: To study three atypical glioneuronal tumours (GNTs), in order to shed light on the clinical and pathological features of this diverse tumour group.

Methods And Results: Clinical and neuropathological data for each case were retrospectively reviewed. Case 1 involved a 17-year-old boy with left leg movement difficulty. A mass lesion in the basal ganglia was detected radiologically; histopathological features included neurocytic/perivascular rosettes and a pilocytic astrocytoma component. Case 2 involved a 33-year-old man with intractable epilepsy. His left parietal lobe contained a cyst-like mass, resembling dysembryoplastic neuroepithelial tumour and rosette-forming glioneuronal tumour of the fourth ventricle microscopically. Case 3 involved a 21-year-old woman with a mass lesion in the mesencephalic tegmentum extending to the third and fourth ventricles and the suprasellar region. The lesion contained perivascular/neurocytic rosettes and an oligodendroglioma-like component. None of the tumours expressed an isocitrate dehydrogenase I mutation of the R132H type or contained a 1p/19q deletion, a BRAF(V600E) mutation, or KIAA1549-BRAF fusion.

Conclusions: We describe three GNTs with atypical histopathology and locations. Additional cases and molecular studies are needed to better understand the biological nature of GNTs and to refine their classification system.