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.

Monomorphous angiocentric glioma: a distinctive epileptogenic neoplasm with features of infiltrating astrocytoma and ependymoma.

We present 8 examples of a neoplasm with features of both astrocytoma and ependymoma that may represent a distinct clinicopathologic entity. The cerebral hemispheric tumors occurred in patients that were 3, 4, 12, 14, 15, 26, 30, and 37 years of age. All presented with seizures that, with the exception of 2, began in childhood. Magnetic resonance imaging studies showed ill-defined, T2-hyperintense, generally noncontrast-enhancing lesions that, although centered on the cortex or amygdala, extended into the underlying white matter for a short distance. Histologically, the variably infiltrative tumors were distinctively angiocentric with well-developed perivascular pseudorosettes in some cases. Longitudinal and/or circumferential orientations of perivascular cells were common also. The cells were uniform in their cytologic features from case to case and were bipolar in all but one case. A glial nature was inferred from immunoreactivity for GFAP, and ependymal differentiation was suggested by positivity for EMA in three cases and ultrastructural features in one. Overall, the tumors were biologically indolent except for one that recurred and ultimately proved fatal.