Pneumothorax due to hemangiopericytoma metastasis from the thigh.

A 25-year-old female had malignant hemangiopericytoma of the right thigh resected. Three years later, right pneumothorax developed, necessitating a thoracotomy. A 3-cm bulla was discovered on the lower right pulmonary lobe and was subsequently resected. Microscopy showed tumor cells which were positive for actin, but negative for epithelial membrane antigen, vimentin, and factor VIII-related antigen--features compatible with those of the thigh. The patient has been free of the disease for five years. Pertinent literature reveals similar cases with hemangioendothelioma but offers few reports on pneumothorax caused by metastatic hemangiopericytoma.