The high mitotic count detected by phospho-histone H3 immunostain does not alter the benign behavior of angiocentric glioma

Angiocentric glioma (AG) has been formally codified in the revised 2007 WHO Classification of Tumours of the Central Nervous System. AGs characteristically exhibit mixed features of ependymal and diffuse astrocytic differentiation and low proliferation rates, with Ki-67 labeling indices ranging from less than 1 to 5%. A single case with anaplastic recurrence and a labeling index of 10% has been reported. In the present study, we report a series of three AGs (Case 1: 4-year-old girl at right frontal lobe; Case 2: 4-year-old boy at left frontal lobe; Case 3: 9-year-old boy at right temporal lobe). Case 1 with elevated proliferation index (~10%) and increased mitotic activity (six mitoses per 10 high-power fields) on phospho-histone H3 (pHH3) immunostain at presentation, nonetheless, has shown protracted recurrence-free survival after 6 years of follow-up. So far, this is the first report for evaluating the mitotic activity in AGs using pHH3 immunostain.