Glioblastoma multiforme versus pleomorphic xanthoastrocytoma with anaplastic features in the pathological diagnosis: a case report

Abstract

Background: Pleomorphic xanthoastrocytoma (PXA) with anaplastic features should be strictly distinguished from glioblastoma multiforme (GBM).

Case presentation: A case of PXA that was initially diagnosed as GBM is presented. A 42-year-old man visited our clinic because of right hemiparesis and total aphasia. Head magnetic resonance imaging demonstrated enhanced multiple cystic lesions in the left temporal lobe suggesting an intra-parenchymal brain tumor. The lesion was partially removed and GBM with a Ki-67 index of 20 % was diagnosed by pathological examination of the resected specimen. Despite receiving radiation and chemotherapy, the patient died 6 months after the first admission. At autopsy, the boundary between the tumor and normal brain tissue was clear. Large parts of the tumor demonstrated typical features of PXA, including pleomorphism, clear xanthomatous cells with foamy cytoplasm, positive silver staining, and a Ki-67 index of less than 1 %.

Discussion and conclusions: GBM should be diagnosed only when the majority of the tumor cells are undifferentiated. Although the operative specimen appeared typical GBM histologically, the diagnosis of GBM was subsequently excluded by the autopsy finding that much of the tumor had the characteristic features of a benign PXA. Therefore, the final diagnosis in this case was PXA with anaplastic features. PXA with anaplastic features should be carefully distinguished from GBM to facilitate appropriate decisions concerning treatment.

Keywords: Anaplastic features; Glioblastoma; Ki-67 index; Pleomorphic xanthoastrocytoma.

Fig. 1

a MRI before biopsy. T1-wighted image (T1WI) shows multiple cystic lesions in the left temporal lobe causing a left to right midline shift. These cysts are displayed as high signals in T2-weighted image (T2WI) and low signals in diffusion weighted image (DWI). T2WI also demonstrate edematous brain tissue around the cysts, some parts of which shows high signals in DWI. The cyst walls and surrounding tissue are definitely enhanced by gadolinium dimeglumine (lower line). White arrows indicate the enhanced portion from which the biopsy was taken. b Pathological findings on biopsy. Hematoxylin and eosin (HE) stained section showing high cellularity and dysplasia with endothelial proliferation in the lesion (a). Giant cells and pseudo-rosettes are also identifiable (b black arrow), and areas of necrosis sections are present (c). The highest Ki-67 index is 20 % (d)

Fig. 2

MRI 3 months after treatment The size and number of the cystic lesions have increased with a pronounced left to right midline shift demonstrating impending cerebral herniation. Enhanced lesions still localized surround the cysts and there is no evidence of tumor extension into the basal ganglia or corpus callosum

Fig. 3

Pathological findings on autopsy. a Macroscopic observation of the brain shows tumor tissue only close to the cysts without aggressive invasion of deep white matter. b Necrosis is clearly apparent in the tumor (black arrow). c Higher magnification of the tumor tissue showing it has well-defined boundaries (a, b, c). Pleomorphism of the tumor with giant cells is readily apparent (d). Clear xanthomatous cells with foamy cytoplasm are visible (black arrowheads) in the pleomorphic portion of the tumor (e), and the area is strongly positive on silver staining (f). The tumor is strongly positive for glial fibrillary acidic protein (g) and the Ki-67 index is extremely low as 1 % (h)