Pulmonary metastasizing hemangiopericytoma.

Hemangiopericytomas are rare tumors, originating from pericytes of the small vessels, that can appear anywhere in the body. From the histological picture it is difficult to determine whether or not they are malignant. The metastasizing rate depends upon the tumor's location and varies from 50 to 80%. Local recurrences occur in roughly 50% of the cases. Hemangiopericytoma is normally surgically treated because radio- and chemotherapy are generally less effective. There is limited experience in treating metastasizing hemangiopericytomas with chemotherapy. We treated 2 patients with pulmonal metastasizing hemangiopericytoma: In 1, the tumor originated in the brain and in the other, the left knee. Both patients had chemotherapy over an extended period of time. By means of x-ray, histological, and electronmicroscopical examinations we report on the course of the diseases.