Angiocentric glioma: report of clinico-pathologic and genetic findings in 8 cases.

ABSTRACT

Angiocentric glioma has recently been described as a novel epilepsy associated tumor with distinct clinico-pathologic features. We report the clinical and pathologic findings in 8 additional cases of this rare tumor type and extend its characterization by genomic profiling. Almost all patients had a history of long-standing drug-resistant epilepsy. Cortico-subcortical tumors were located in the temporal and parietal lobes. Seizures began at 3 to 14 years of age and surgery was performed at 6 to 70 years. Histologically, the tumors were characterized by diffuse growth and prominent perivascular tumor cell arrangements with features of astrocytic/ependymal differentiation, but lacking neoplastic neuronal features. Necrosis and vascular proliferation were not observed and mitoses were sparse or absent. MIB-1 proliferation indices ranged from <1% to 5%. Immunohistochemically, all cases stained positively for glial fibrillary acidic protein, vimentin, protein S100B, variably for podoplanin, and showed epithelial membrane antigen-positive cytoplasmic dots. Electron microscopy showed ependymal characteristics in 2 of 3 cases investigated. An analysis of genomic imbalances by chromosomal comparative genomic hybridization revealed loss of chromosomal bands 6q24 to q25 as the only alteration in 1 of 8 cases. In 1 of 3 cases, a high-resolution screen by array-comparative genomic hybridization identified a copy number gain of 2 adjacent clones from chromosomal band 11p11.2 containing the protein-tyrosine phosphatase receptor type J (PTPRJ) gene. All patients are seizure free and without evidence of tumor recurrence at follow-up times ranging from 1/2 to 6.9 years. Our findings support 2 previous reports proposing that angiocentric glioma is a novel glial tumor entity of low-grade malignancy.