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

AIMS: To review the clinicopathological spectrum and evolution of the histology of pleomorphic xanthoastrocytomas (PXAs) seen at a single children's hospital. METHODS: PXAs were selected from the Royal Children's Hospital archives over 30 years. The clinical features and pathology were reviewed, specifically checking the histological variation between areas, and the changes between biopsies. RESULTS: Fifteen patients were identified. Ten had repeat biopsies. Eleven patients did not show histological features of anaplasia. Of these eleven, three did not show the characteristic histological features, which developed 3 and 11 years later in repeat biopsies in two. Seven showed uncommon potentially confusing histology. One died, one had stable disease and one had progressive disease. Three with incomplete initial surgery remained in complete remission following more surgery, radiotherapy and chemotherapy when the tumours progressed, up to 11 years later. Four patients did show anaplasia, with abrupt change from typical PXA in two, and years following initial biopsy in one. Of these four patients, three died, one with extensive metastasis. CONCLUSIONS: PXA should be considered in superficial cerebral tumours composed only of compact bundles of glial fibrillary acidic protein positive spindle cells with inconspicuous mitosis, even when the highly characteristic features of this tumour are not seen. The prominent variation in histology makes small biopsies difficult for diagnosis and assessing anaplasia. Patients with non-anaplastic tumours can often be salvaged by more treatment for tumour progression.