Sarcomatoid transformation of a pleomorphic xanthoastrocytoma

Abstract

Pleomorphic xanthoastrocytoma (PXA) is an uncommon, superficially situated astrocytic tumour typically occurring in children and young adults and characterised by cellular pleomorphism and frequent xanthomatous change. Classic forms of PXA are WHO Grade II but not all PXA follow a ‘benign' course. Recurrence is common, occurring in 72% of patients within 5 years. Overall survival is estimated at 81% at 5 years and 70% at 10 years. An estimated 15– 20% of PXA demonstrate anaplastic features and around 10% develop overtly malignant features histologically indistinguishable from glioblastoma. 1 The issue of WHO grading of PXA with anaplastic or malignant transformation is unresolved, however many authors use WHO Grade III or IV presumptively. 2 , 3 We describe a case of pleomorphic xanthoastrocytoma with ana-plastic features ina 41-year-old female which demonstrated multiple recurrences over a period of 9 years culminating in transformation to high grade gliomawith sarcomatoidareas.These areasdemonstrated interlacing fasciclesofatypical spindled cells, high mitotic index and focal necrosis and showed positive immunohistochemical staining for smooth muscle actin and pan-actin with relative loss of GFAP expression. The development of sarcomatoid features heralded the onset of more aggressive behaviour, with local recurrence, devel-opmentofmultiple spinal metastases and demise12months later. To our knowledge this pattern of malignant transformation within PXA has only been described once previously. 4