Primary intracranial haemangiopericytoma: comparison of survival outcomes and metastatic potential in WHO grade II and III variants.

Primary intracranial haemangiopericytomas (HPC) are rare, highly vascular tumours with a high propensity for local recurrence and distant metastasis. Optimal treatment includes maximal surgical resection followed by adjuvant radiotherapy. In 2007, new histopathological grading criteria were introduced to differentiate between high grade (World Health Organization [WHO] grade III) and low grade (WHO grade II) tumours. Given the rarity of this tumour, there is a paucity of information regarding the prognostic significance of histological grade. We conducted a retrospective review of our 20 year experience in treating 27 patients with HPC at our institution. Statistical analysis to compare overall survival, local recurrence rate and metastatic potential between the two grades were conducted using Kaplan-Meier analysis. The estimated median survival for grade II HPC was 216 months and for grade III tumours was 142 months. On multivariate analysis, grade II tumours were associated with better survival than grade III lesions (hazard ratio=0.16, 95% confidence interval 0.26-0.95; p=0.044). During the study period, 33% of grade III tumours developed local recurrence compared to 21% of grade II tumours. Metastases were found in 36% of grade II patients and 25% of grade III patients. There was no significant statistical difference in local recurrence rate and metastasis between the two grades. Higher histological grading in HPC is associated with worse overall survival. However based on our series higher histological grading is not associated with higher local recurrence or distant metastatic rates.