{'fraction_non_alphanumeric': 0.025891829689298044, 'fraction_numerical': 0.013521288837744535, 'mean_word_length': 5.4748603351955305, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Clinical, histological and imaging aspects of pleomorphic xanthoastrocytomas: the key is in the name.

Pleomorphic xanthoastrocytoma (PXA) is a rare tumor of the central nervous system, first described in 19791. It was added to the World Health Organization (WHO) classification of tumors in 19932. First reports emphasized that despite their highly pleomorphic and bizarre cytology, which suggested a malignant behavior, these tumors appeared to have a relatively favorable prognosis in most of the cases1, with a 75% overall survival at 5 years3. PXA were probably some of the first tumors in whose characterization immunohistochemical markers were essential. Namely, the demonstration of glial fibrillary acidic protein (GFAP) led to the definition of PXA as a new clinicohistopathologic tumor entity of astrocytic nature1. Prior to its initial description, PXA was often classified among giant cell glioblastomas or mesenchymal tumors such as fibrous xanthomas or sarcomas (due to its rich reticulin network)4. In the following years, clinical and surgical series were reported5; patients with PXA typically present as children or young adults with almost 70% under 30 years of age, and equal frequency of occurrence in both males and females4,6. Presenting symptoms consist primarily of seizures, often of long duration3,4; followed by dizziness, headache and focal neurological deficit6. Studies focusing on imaging aspects of PXA demonstrated that these tumors are often superficial with leptomeningeal extension and involve the temporal lobe most frequently (up to almost 50% in a large series)4; other common locations include the parietal, frontal, and occipital lobes. Patterns of presentation can be purely cystic (uni or multilocular), mixed cystic-solid and purely solid; the solid portions usually enhance intensely after the use of contrast material6,7. Remodeling of the adjacent calvarium can be appreciated, related to the slow growth of this superficial lesion. Surgery is clearly the treatment of choice, and the extent of primary resection has great impact on prevention of recurrence and survival rates. Cases in which a gross total removal is achieved, a “wait and see” approach can be recommended followed, if necessary, by additional surgery for residual and/or recurrent tumor4. At present, the role of adjuvant radiotherapy and/or chemotherapy remains uncertain, but it seems that patterns of care are following the treatment patterns of gliomas3. More recently, unusual aspects pertaining PXA started to be reported, such as atypical locations (especially in the posterior fossa and spine4,8) and an association with neurofibromatosis type I9. Uncommon histological aspects include descriptions of PXA in conjunction with ganglioglioma, dysembryoplastic neuroepithelial tumor, oligodendroglioma and even cortical dysplasia10,11. This finding led some authors to speculate about the histogenesis of PXA as deriving from bipotential precursor cells, in opposition to previous analyses that proposed mesenchymal precursors or a subclass of astrocytes as the tumor origin12. Prognosis seems to be worse than initial reports in a subset of patients. Although PXA is considered a WHO grade II tumor, anaplastic transformation can occur in up to 15 to 20% of MD, PhD; Neuroradiologist. Instituto de Radiologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (USP); Centro de Diagnósticos Brasil (CDB), São Paulo SP, Brazil.