[A voluminous prevesical hemangiopericytoma. A clinical case report].

Hemangiopericytoma is a rare and solitary solid tumor originating from pericytes, which are contractile pericapillary cells, first identified and described by Zimmermann in 1923. Although macroscopically the aspect is benign, this tumor has a recognised ability for local invasion and distant dissemination. The authors describe the case of a patient affected with giant prevesical hemangiopericytoma. Echographic and computed tomographic scans have been fundamental in defining location and size of the neoplasma as well as its relations to the surrounding structures. The authors emphasize the difficulty of reliably predicting the biological behaviour of these tumors and the necessity for radical surgery.