Hemangiopericytoma: A Rare and Challenging Lesion of the Skull Base

Introduction: Solitary fibrous tumors have been recognized for almost 100 years, usually taking origin from the pleura. The recent advent of immunohistochemistry has allowed a separation of these into various lesions including hemangiopericytomas. These are thought to arrive from Zimmerman pericytes around capillaries in mesenchymal tissue. Although the earliest of these were recognized as serosal origin, it is clear that these can occur involving the skull base including the paranasal sinuses, the parasellar region, and the orbit. Although usually surrounded by a pseudo capsule, the highly vascular nature of these lesions makes surgery challenging.

Materials and Methods: A review of two hemangiopericytomas involving the skull base illustrates some of the challenges of surgical intervention and highlights some of the potential options for additional therapy.

Results: Although endoscopic techniques have been used to completely excise paranasal sinus and skull base for hemangiopericytomas, the highly vascularized nature has made these a challenge indicating that in at least some cases an open approach with wide exposure may have advantages. Clearly immunohistochemistry allows for better segregation of these lesions. This has implications in terms of aggressiveness, occurrence rates, and malignant transformation with possible metastatic disease.

Conclusion: Although fine needle aspiration biopsy has been reported to be of benefit, often a biopsy of these is necessary to make a definitive diagnosis associated with immunohistochemical staining. These tumors remain a significant challenge with a not insignificant recurrence rate and an uncommon, but not rare, transformation to a more aggressive form.