Aggressive malignant hemangiopericytoma in the neck.

Hemangiopericytomas are rare vascular tumors, one fourth of which occur in the head and neck. These lesions are characteristically slow growing and slow to metastasize. We describe an otherwise healthy patient with a hemangiopericytoma on the left side of his neck that metastasized to his chest wall within 3 months after the tumor was first observed. The metastasis occurred while the patient was receiving radiation therapy. The patient died soon afterward. This case illustrates the aggressive malignant potential of hemangiopericytomas.