Pediatric cerebellar pleomorphic xanthoastrocytoma with anaplastic features: a case of long-term survival after multimodality therapy

A 4-year-old girl had a large midline cerebellar solid and cystic mass partially attached to the meninges. The original diagnosis was glioblastoma multiforme and she was treated by a gross-total surgical resection followed by chemotherapy and radiation theraphy to the posterior fossa during the ensuing 14 months. She has received no further theraphy and appears to be doing well 12 years later. This unusual favorable clinical outcome prompted our review of this case. Additional special stains and immunocytochemistry were performed on the paraffin embedded tumor sections. We have confirmed the original histopathological observations of hypercellularity and focal nuclear pleomorphism, atypical mitoses, vascular hyperplasia, as well as focal necrosis. However, the additional stains revealed that the tumor is a relatively well-circumscribed meningeal-based astrocytic tumor (positive for GFAP) with extensive reticulin deposit and focal neuronal differentiation (positive for synaptophysin). A Ki67 labeling index is generally very low, but is positive in up to 5-10% of tumor cells focally. In the light of the favorable clinical outcome and the overall histological features, this tumor may be best reclassified as a rare example of cerebellar pleomorphic xanthoastrocytoma with foci of anaplasia.