Angiocentric glioma mimicking encephalomalacia

Abstract

Angiocentric glioma is a rare low-grade neoplasm of the central nervous system which typically presents with medication-refractory seizures in children and young adults. On magnetic resonance imaging, angiocentric glioma is classically T1 hypointense and T2/FLAIR hyperintense. We present the case of a 40-year-old male who had been followed by our institution for 17 years for management of epilepsy. Initial and repeat brain imaging showed an apparent region of cystic encephalomalacia in the right frontal lobe. In an attempt to control his seizures, the lesion was resected. Grossly, the cut surface of the specimen was characterized by multiple small cystic spaces. Microscopically, the lesion was composed of an infiltrative population of glial cells variably arranged in perivascular "pseudorosettes," nodules, and subpial "palisades." The final diagnosis was angiocentric glioma. This is the second reported case of an angiocentric glioma mistaken for encephalomalacia.

Keywords: Angiocentric glioma; Encephalomalacia; Low-grade glioma; Seizures.

Fig. 1

Axial noncontrast head CT (A; patient age 25 years) shows a hypoattenuating lesion in the right frontal lobe, involving the cortex and underlying white matter, with no appreciable mass effect, initially interpreted as encephalomalacia and gliosis. Axial (B) and coronal (C) T2-weighted images show that the right frontal lobe lesion has very hyperintense signal and involves the cortex and subcortical white matter. Axial T1-weighted image (D) shows that the lesion is predominantly hypointense but has subtle hyperintense signal at its periphery. The coronal FLAIR (E) image shows that the lesion has predominant hypointense FLAIR signal centrally but has a FLAIR hyperintense rim. (Images B-E, patient age 39 years) Axial PET (F; patient age 39 years) shows that the right frontal lesion is not FDG avid, a finding consistent with encephalomalacia.

Fig. 2

The neoplasm is composed of multiple cystic spaces (A, hematoxylin and eosin, original magnification ×20) lined by elongate tumor cells, which are frequently arranged around blood vessels forming perivascular “pseudorosettes” (B, hematoxylin and eosin, original magnification ×200). Occasional nodules composed of spindle cells in fascicles, reminiscent of schwannoma, are present (C, hematoxylin and eosin, original magnification ×200). Tumor cells form palisades along the subpial surface of the brain (D, hematoxylin and eosin, original magnification ×200). The neoplastic cells are immunoreactive for GFAP (E, GFAP, original magnification, ×400), and cytoplasmic dot-like microlumen-type staining is seen on EMA stain (F, EMA, original magnification ×600). (Scale bars: A, 2 mm; B, C, D, 200 microns; E, 100 microns; F, 50 microns.)