Angiocentric glioma: a report of nine new cases, including four with atypical histological features

Angiocentric glioma (AG) is a rare, slow-growing tumour of the central nervous system. It is often associated with refractory epilepsy and occurs most commonly in children and young adults. We herein report nine cases of AG, including four with atypical histological findings.The clinical data and clinicopathological findings of nine cases with AG histological features were described.All nine patients had a history of refractory epilepsy with a mean history of 4.4 years and a median age of 17.6 years at surgery. The AG lesions were located in the superficial cerebrocortical region. Histological examination of these cases revealed characteristic structural features of AG, including bipolar spindle-shaped cells with an angiocentric growth pattern. However, four cases also exhibited atypical histological features: one had astroblastoma-like characteristics, two had a distinct cystic region with an onion-like structure and myxoid changes, and the other one had a region involving many abnormal neurones reminiscent to ganglioglioma. All were positive for glial fibrillary acidic protein and vimentin. Eight cases were positive for epithelial membrane antigen (EMA), with a dot-like staining pattern. A diffuse D2-40 staining was visible in these cases, with two having similar staining pattern to EMA. All cases were immunonegative for BRAF V600E and isocitrate dehydrogenase-1 R132H mutations.Our results demonstrate that atypical histological features can be present in AG. A collection of more cases and further molecular analyses are required to confirm our findings.