Malignant Transformation of Pediatric Low-grade Gliomas: Report of Two Cases and Review of a Rare Pathological Phenomenon.

Low-grade gliomas (LGGs) are the commonest benign central nervous system (CNS) tumors seen in children. Unlike LGGs in adults, pediatric LGGs rarely undergo malignant transformation. The incidence of malignant transformation of LGGs in the pediatric population has been reported to be up to 10%. Of these, a few patients have demonstrated this phenomenon even without adjuvant radiation therapy. We report two such unusual cases. A 7-year-old girl presented with a left temporal lesion that was operated upon and was reported as pilocytic astrocytoma (WHO grade I). She presented with a malignant transformation of the tumour 8 years later. The second case was a 10-year-old boy, who had a left frontoparietal ganglioglioma (WHO grade I) that demonstrated malignant transformation to an anaplastic ganglioglioma (WHO grade III) 10 months after the initial surgery. Multiple studies have thrown light on the molecular genetics behind malignant transformation of LGGs in children. These genetic changes can perhaps serve as targets for potential future therapeutic interventions. It is important that patients with LGGs at risk of malignant transformation must be identified early so that a more aggressive treatment strategy can be adopted.

Anaplastic hemangiopericytoma in the frontal horn of the lateral ventricle.

Intracranial hemangiopericytomas are uncommon tumors, and their intraventricular occurrence is even rarer. We report a 40-year-old man who presented with raised intracranial pressure. His MRI showed a 3.3 × 3.2 × 3.2 cm heterogeneously enhancing lesion in the left frontal horn obstructing the foramen of Monro and causing hydrocephalus. The tumor was excised through an anterior interhemispheric, transcallosal approach, and histopathology revealed an anaplastic hemangiopericytoma (World Health Organization grade III). To our knowledge this is the first report of this rare pathology being located within the frontal horn of the lateral ventricle.