Background Pleomorphic xanthoastrocytomas with anaplastic features (PXA-As) are rare tumors about which little is known regarding clinicopathological and molecular features. Several studies have identified BRAF V600E mutations in PXA-As, but the percentage with mutation may differ between adult and pediatric examples, and limited information exists about immunohistochemistry for IDH1 (isocitrate dehydrogenase 1). Design: 10 cases of adult PXA-As seen at our institution since 2000 were assessed for BRAF V600E mutation by polymerase chain reaction testing (PCR) and IDH1 by immunohistochemistry. Results Patients ranged in age from 18-68 years; 4 PXA-As affected temporal lobe and 2 were cystic. Four patients underwent gross total resection; and 9/10 received cranial irradiation and/or adjuvant chemotherapy. Five survived less than 5 years, although 2/5 died from non-tumor causes. Four long-term survivors are alive at 7.5, 9.8, 11.4, and 11.9 years post-diagnosis. 2 of 4 long term survivors had BRAF V600E mutation: patients were ages 18 and 28 years. A 48-year old male without BRAF mutation survives at 9.8 years, even with thalamic location; conversely a 68-year-old female with temporal lobe tumor and BRAF mutation survived 1.9 years after diagnosis. All tumors were IDH1 immunonegative. Conclusion This case series details clinicopathological features of a subset of rare PXA-As in adults. BRAF V600E mutation was identified in 50% of these cases.

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