Brain surface spindle cell glioma in a patient with medically intractable partial epilepsy: a variant of monomorphous angiocentric glioma?

We report a case of brain surface angiocentric glioma in a 6-year-old Japanese boy with medically intractable partial epilepsy. MRI showed somewhat ill-defined high-signal lesions on fluid-attenuated inversion recovery and T2-weighted imagings of the right occipitoparietal cortex. At surgery, a yellowish tumor was localized in the superficial cortex. Histologically, the tumor was predominantly composed of elongated astrocytic cells forming rings around blood vessels. Tumor cells circumferential to vessels predominanted in low cellurarity areas, whereas radial alignment with perivascular pseudorosettes was observed in more cellular regions. These perivascular pseudorosettes closely resembled those of ependymoma. The tumor cells showed variable cytoplasmic immunoreactivity with GFAP. These findings were more likely monomorphous angiocentric glioma, which was first described by Wang et al. in 2005. However, in our case the tumor had a small foci of polymorphous appearance and a comparatively high MIB-1 labeling index (8%). Therefore, the present case may be an atypical form of monomorphous angiocentric glioma. However, no de novo anaplastic monomorphous angiocentric glioma similar to our case has yet been reported in the literature. It remains to be determined whether the behavior of monomorphous angiocentric glioma is an example of benign biological characteristics or whether it more closely resembles a low-grade malignant tumor.