Pleomorphic xanthoastrocytoma: MR imaging findings in 19 patients

Abstract

Background Pleomorphic xanthoastrocytoma (PXA) is a rare and special type of astrocytoma which occurs in childhood and adolescence, and usually with a favorable prognosis. Since its initial description, PXA cases have been reported infrequently in the literature, mostly as single cases or small series. Purpose To review the imaging characteristics of PXA. Material and Methods MR imaging findings of 19 pathologically confirmed PXAs were retrospectively analyzed and correlated with the clinical and pathological features. Results The clinical presentation in 18 patients included: dizziness (8); headache (9); and epilepsy (8). One patient was asymptomatic. On MR imaging, the tumors were located in the brain surface (17), thalamus (1) or deep in the right frontal lobe (1). The tumors were cystic (4), mixed cystic-solid (7), or solid (8) with well-defined (11) or poorly-defined borders (8). Peritumoral edema was marked (8), mild (9) or absent (2). Cystic components of tumors were hypointense on T1- and hyperintense on T2-weighted images whereas the solid components of tumors were hypointense or isointense on T1- and slightly hyperintense on T2-weighted images. There was marked (10), moderate (7) or no (2) contrast enhancement in the solid tumors with surrounding leptomeningeal enhancement (7). The tumors were located in the frontal lobes (8), temporal lobes (7), occipital lobe (1), cerebellum (1), thalamus (1), and sellar region (1). Histologically, 18 tumors were classified as WHO grade 2 comprising of pleomorphic giant cells, spindle cells and foamy cells. One PXA with anaplastic features was composed of pleomorphic polygonal cells and spindle cells, and with high mitotic activity ( ≥5 mitoses per 10 HPF). Immunohistochemical reactions to glial fibrillary acidic protein (GFAP) were positive in all 19 cases. Conclusion The pathological appearances of PXA are distinctive. MR imaging could display the morphologic features exactly, and has important diagnostic value for PXA.