CT and MR features of primary pulmonary hemangiopericytomas.

We investigated the radiological findings of four patients with malignant pulmonary hemangiopericytomas, comparing plain chest radiography, CT, and MR. The radiographic presentation ranged from a small single lesion to a tumor almost completely occupying a hemithorax. Pathognomonic radiological features of malignant pulmonary hemangiopericytomas could not be established, but characteristic features include a large lobulated well-circumscribed mass with an encapsulated appearance, contrast enhancement of the margin, and no signs of surrounding compression atelectasis. The tumors were associated with late onset or a paucity of chest symptoms. Additional information regarding heterogeneity and effects on adjacent structures was provided by MR and was helpful in suggesting the diagnosis of malignant pulmonary hemangiopericytoma.