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  • Updated 11.30.2020
  • Released 02.16.1999
  • Expires For CME 11.30.2023

Pleomorphic xanthoastrocytoma

Introduction

Overview

Pleomorphic xanthoastrocytoma (PXA) is a rare subtype of low grade glioma that affects predominantly a pediatric and young adult population. Theses tumors frequently arise in the temporal lobes and often present with seizures. This review covers the latest developments in our understanding of pleomorphic xanthoastrocytoma, including its more aggressive anaplastic variant, the ability of low grade form to transform into a high grade form, and the new efforts to classify unique molecular alterations.

Key points

• Pleomorphic xanthoastrocytoma (PXA) is a WHO grade 2 neoplasm that is most often diagnosed in children and young adults.

• An anaplastic variant exists with poorer overall prognosis; furthermore, classic pleomorphic xanthoastrocytoma (WHO grade 2 PXA) has the potential for malignant transformation into a high grade glioma (WHO grade 3 PXA).

• WHO 2016 criteria define anaplastic pleomorphic xanthoastrocytoma by the presence of 5 or more mitotic figures per 10 high-power microscopic fields (0.23 mm2 field size). Necrosis may be present, but alone does not raise the grade.

• Epilepsy is the most common presentation.

• Pathologic features include nuclear and cytoplasmic pleomorphism, xanthomatous changes, multinucleated cells, presence of pericellular reticulin, and eosinophilic granular bodies (EGBs).

• Pleomorphic xanthoastrocytoma has the potential to spread via the cerebrospinal fluid (CSF).

• WHO grade is a prognostic factor. Presence of V600E BRAF mutation is also a prognostic factor. Extent of resection also has important implications for prognosis.

• The majority of cases have been shown to harbor CDKN2A/B homozygous deletions and MAPK pathway alterations, the most common of which is the BRAF V600E mutation.

Historical note and terminology

Pleomorphic xanthoastrocytoma (PXA) is a rare astrocytic tumor. The first cases were reported in 1973 as meningocerebral fibrous xanthomas, which were presumed to be of mesenchymal origin (26). In 1978, the discovery of the astrocytic marker GFAP allowed Kepes and coworkers to reevaluate these previously reported cases, along with several new ones, and to confirm their astrocytic lineage. Their subsequent report of 12 patients with pleomorphic xanthoastrocytoma was the first to systematically describe its features and to name this new entity—one that reflects its most salient pathologic characteristics (27). An evaluation of a pleomorphic xanthoastrocytoma excised in 1930 from a patient who survived for 40 years has yielded what is apparently the earliest known example of this tumor (12). The recognition of this tumor is critical for patient care because of the difference from the natural history of most astrocytic tumors and the consequent implications for management. Moreover, identification of the targetable molecular alterations can help define subtypes of this tumor and offers new potential treatment avenues.

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