[1782] Pathologic Features of Pleomorphic Xanthoastrocytoma, Conventional and Anaplastic: A Single Tertiary-Care Oncology Centre Experience

Munita Meenu Bal, Sridhar Epari, Shubhada Kane, Sona Pungaonkar, Aliasgar Moiyadi, Prakash Shetty, Tejpal Gupta, Neha Lanke, Rakesh Jalali. Tata Memorial Hospital, Mumbai, Maharashtra, India; Nanavati Hospital, Mumbai, Maharashtra, India

Background: Pleomorphic xanthoastrocytoma (PXA) is an uncommon low-grade glial neoplasm associated with favorable outcome. However, a subset of cases display aggressive histology and are referred to as PXA with anaplastic features (APXA). The aim of this study was to review the clinical and pathological features of conventional PXA and APXA cases.
Design: Paraffin blocks and slides of all consecutive cases of PXA accessioned during a 9 year period were retrieved. Histology was reviewed and diagnosis confirmed according to WHO 2007 classification. Clinical, radiological and follow-up details were obtained from electronic medical records and patients' files.
Results: A total of 39 cases were studied, comprising 31 PXA, grade II (79%) and 8 APXA (21%) cases. Median age was 19 years. Male-to-female ratio was 1.6:1. Temporal lobe was the commonest site involved. Rare occurrences in cerebellum and spinal cord were also observed in 2 and 1 cases, respectively. Out of 31 PXA cases, 3 cases revealed atypical morphological features of extensive microvascular proliferation (MVP) and MIB-1 labeling>10% superimposed upon classical features of PXA. Six out of 8 APXA cases were denovo while 2 evolved from a pre-existing grade II PXA. Prior radiation was given in the 2 secondary APXA cases. Histologically, APXA cases were characterized by conventional PXA areas with additional presence of necrosis, MVP, augmented mitoses (mean, 8/10 HPF) and MIB-1 labeling indices (mean, 18%). Additionally, a few APXA tumors exhibited a preponderant epithelioid histology (4), rhabdoid phenotype (2) and an angiocentric pattern (1). Presence of MVP and MIB-1>10% was observed in the 2 primary grade II PXAs tumors that subsequently evolved to secondary APXA. Immunohistochemistry revealed S-100, focal GFAP and CD34 reactivity and absent p53 expression. Follow-up ranged from 3-47 (median, 29 months). Recurrence rate in PXA, grade II and APXA was 12% and 75%, respectively.
Conclusions: PXAs are unique glial neoplasms with a distinctive clinical and pathological profile. APXAs are higher grade PXAs that display aggressive histology and proclivity towards early recurrences and worse outcome. Microvascular proliferation and MIB>10% appear to be a harbinger of an impending transformation of grade II PXA to APXA.
Category: Neuropathology

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 259, Tuesday Afternoon


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