Glioblastoma multiforme versus pleomorphic xanthoastrocytoma with anaplastic features in the pathological diagnosis: a case report
© The Author(s). 2016
Received: 13 January 2016
Accepted: 8 July 2016
Published: 22 July 2016
Pleomorphic xanthoastrocytoma (PXA) with anaplastic features should be strictly distinguished from glioblastoma multiforme (GBM).
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.
KeywordsPleomorphic xanthoastrocytoma Glioblastoma Anaplastic features Ki-67 index
The characteristic histological features of pleomorphic xanthoastrocytoma (PXA) include strong pleomorphism resembling that of glioblastoma multiforme (GBM); however, according to the WHO classification, failure to identify mitosis and necrosis should result in a diagnosis of PXA, which is classified as a grade II glial tumor . The prognosis of PXA is relatively favorable; however, malignant transformation with aggressive clinical behavior has been reported in some recurrences [2, 3]; transformation to GBM has also been described . When anaplastic components are identified in a tumor, the diagnosis is PXA with anaplastic features [5, 6]. We here present a case in which we believe the diagnoses of malignant transformation of PXA or PXA with anaplastic features were both inappropriate, because only the characteristic features of GBM were found on histological examination of the initial specimen, a partially resected tumor, whereas PXA was diagnosed at autopsy, when the entire tumor could be carefully examined.
The tumor was partially removed and the largest cyst opened under general anesthesia (the white arrows in Fig. 1A indicate the resected portion.). The tumor was yellowish and soft and the fluid in the cyst was weakly xanthochromic. Histological examination of the resected tissue resulted in a diagnosis of GBM (Fig. 1B).
Pathological findings on biopsy
Histological examination of the operative specimen resulted in a diagnosis of GBM, and this diagnosis was based on the following characteristic features; high cellularity, pleomorphism with giant cells, endothelial proliferation, pseudo-rosette formation, necrosis (Fig. 1B a, b, c), and a high Ki-67 index of 20 % (Fig. 1B d).
Histological findings on autopsy
Malignant tumors contain areas of different malignant grades. The most malignant grade determines the grade for the entire tumor, even when most of the tumor is of lower grade [8, 9]. According to this rule, our patient’s tumor was a grade IV GBM, which is in accordance with his short survival of 6 months from the first admission.
However, we considered that the diagnosis of GBM is incorrect in our case for the following reasons: (i) the features identified on MRI, in particular the multiple cystic lesions with little intervening parenchyma and minimal invasion to the basal ganglia, are not typical of GBM and (ii) histological examination of autopsy specimens demonstrated typical PXA with well-defined boundaries between the tumor and the surrounding normal brain tissue and the highest Ki-67 index was 1 %. A decrease in median Ki-67 index after chemotherapy has been reported in 106 patients with breast cancer, this index decreasing to 5.21 % from 16.68 % . In our case, the Ki-67 index may have been reduced by irradiation and TMZ treatment; however, a drop of the index to 1 % from 20 % seems too pronounced to be attributable to treatment. Additionally, it seems extremely improbable that a GBM, the most malignant brain tumor, would revert to being a benign tumor with treatment.
In our case, the most crucial finding that is incompatible with a diagnosis of GBM is that typical characteristics of PXA were identified in most parts of the tumor at autopsy. According to the histological definition of grade IV glioma, almost 100 % of these tumors is composed of undifferentiated cells and few well-differentiated cells are present . Hirose et al. have stated that anaplastic PXA should be distinguished from GBM by identifying the salient histological features of conventional PXA even in the anaplastic areas . Therefore, after careful consideration, we conclude the correct histological diagnosis in our case is PXA with anaplastic features, even though GBM was diagnosed on histological examination of the original operative specimen.
PXA, pleomorphic xanthoastrocytoma; GBM, glioblastoma multiforme; MMT, manual muscle testing; MRI, magnetic resonance imaging; T1WI, T1-weighted images; DWI, diffusion-weighted images; T2WI, T2-weighted images; TMZ, temozolomide
We express our gratitude to Edanz Group for scientific English editing of this article.
All authors declare that there are no funding sources in this report.
Availability of data and materials
The datasets supporting the conclusions of this article are included in the article.
SMY contributed to the concept and design of the report and writing the article. HM, YT, and MN performed surgery and took care of the patient. SS arranged and performed adjuvant therapies. MT and MK carried out autopsy and histological investigations. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
Consent for publication
Written informed consent for publication of their clinical details and clinical images was obtained from the patient’s family. A copy of the consent form is available for review by the Editor of this journal.
Ethics approval and consent to participate
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