Analysis of p53 mutation and expression in pleomorphic xanthoastrocytoma

C Giannini, MD, PhD a, D Hebrink a, BW Scheithauer, MD a, AP Dei Tos, MD b and CD James, PhD a

a Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, b Department of Anatomic Pathology, Regional Hospital of Treviso, Italy

AIM: Pleomorphic xanthoastrocytoma (PXA) is a rare, superficially situated brain tumor, most often occurring in the temporal lobe of young adults, typically associated with seizures, and having a relatively favorable prognosis. Prior studies have shown TP53 mutations to occur in up to 25% of PXAs. METHODS: We performed immunostains for p53 protein and examined the mutation status of exons 5-8 of the p53 gene in 55 PXAs, 8 of which had undergone one or multiple recurrences. RESULTS: Immunostaining for p53 was observed in <1% of tumor cells in 35 cases (64%), 2-10% in 15 (27%), 11-50% in 4 (7%), and in >50% in1 case (2%). No significant increase in p53 protein expression was noted in recurrent tumors, even when associated with histologic anaplasia. We found a singleTP53 heterozygous mutation in exon 7 in one of 47 primary tumors that yielded useable DNA, as well as in its recurrence 3 years later. This tumor, a grade II PXA, showed no signs of anaplastic transformation upon recurrence. Eleven additional recurrences from 7 patients, 5 of which demonstrated histologic anaplasia, showed no TP53 mutations in exons 5-8. CONCLUSIONS: Based on our data, TP53 mutation is an uncommon (2%) genetic event in PXA formation and does not appear to be involved in tumor progression..

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Risk Assessment, Part 2.