Hemangiopericytoma of the nasal cavity.

Hemangiopericytomas are unusual vascular tumours that rarely occur in the paranasal sinuses and nasal cavity. They are thought to arise from pericytes that surround capillaries, however, there is no proven etiology of these tumours. The diagnosis cannot be made based on gross morphologic characteristics nor on frozen section biopsy. Instead, the diagnosis is dependent on careful histologic examination and reticulum staining. The diagnosis can be confirmed by electron microscopy. The histologic picture is greatly varied from tumour to tumour and within a given tumour itself. The clinical course of hemangiopericytomas ranges from benign to malignant with possible distant metastases and cannot be reliably predicted by histologic criteria. Hemangiopericytomas of the nose and paranasal sinuses are thought to behave less aggressively than those occurring in other parts of the body. Lymph node metastasis is rare and elective neck dissection is not indicated. The accepted treatment of these tumours is wide surgical excision, however adequate surgical margins are usually difficult in the sinonasal region. As a result, hemangiopericytomas can exhibit a high recurrence rate. Therefore, it is mandatory that these patients be followed carefully for the remainder of their lives.