The evolution of the histology in pleomorphic xanthoastrocytomas in children: a study of 15 cases- Introduction

A Special Author Introduction
Pathology
ISSN: 0031-3025 • Frequency: 7/year • Impact Factor 2.673 • Subscribe Now

By C. W. Chow

Pleomorphic xanthoastrocytoma is an uncommon tumour of the brain, occurring mainly in children and young adults, and usually associated with a relatively low grade behaviour in spite of the sometimes alarming morphology. The clinical features, imaging and surgical findings, the highly characteristic histological features, and the changes of anaplasia have been extensively and very well described previously. However there is much variation in the histology of the tumours between patients and between different areas in the same tumour.

In the absence of an independent objective gold standard, such as a molecular event, the diagnosis can be subjective and uncertain if the highly characteristic histology is absent or if there are unusual and potentially confusing features. In this series of 15 cases repeat biopsies were available for study in 10. In two patients the initial biopsies showed a moderately cellular superficial lesion attached to the meninges and composed of compact bundles of spindle astrocytes with occasional mitoses. The highly characteristic features, including the wildly bizarre nuclei with cytoplasmic inclusions, pale hyaline cytoplasm, eosinophilic granular bodies and prominent reticulin fibres, were absent and only noted in the repeat biopsies performed years later.

It is proposed that the features in the pretypical phase in the first biopsies of these two patients, which were also present in all the other cases, at least focally, could be used as the minimum diagnostic criteria, provided there are no exclusion criteria or clear features to suggest other tumours. This pattern is emphasized, as the moderately high cellularity with occasional mitoses could result in misinterpretation as an anaplastic astroyctoma. Confusing features such as prominent neurons, pigmentation and extensive microcystic change and Rosenthal fibres were seen in half the tumours, and can cause diagnostic difficulty with small biopsies. Features of anaplasia were seen in 27% of the cases from this single institution, on presentation in three patients and on follow up in one.

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This article was originally published in Pathology, to read more research in this field please visit: www.rcpa-pathologyjournal.com