Ct and mr features of primary pulmonary hemangiopericytomas

We investigated the radiological findings of four patients with malig-nant 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.