Retroperitoneal and pelvic hemangiopericytomas: clinical, radiologic, and pathologic correlation.

Seventeen cases of hemangiopericytoma of the retroperitoneum were retrospectively analyzed for demographic, morphologic, and radiologic features. These tumors were found in all age groups (2 months to 72 years) and occurred in similar numbers of male and female patients. The tumors tended to be large (11 were greater than 8 cm), were well encapsulated, and occurred less frequently in the pelvic retroperitoneal space (six cases) than in abdominal retroperitoneum (11 cases). All tumors were bulky enough to displace part of the gastrointestinal tract, with only two being inoperable. The most distinctive radiologic feature was hypervascularity (found on 11 of 11 angiograms). Other nondiscriminating radiologic features included well-defined margins and necrosis, with nondistinctive amorphous calcification identified in one case. Angiographic or computed tomographic demonstration of hypervascularity in a retroperitoneal tumor is more suggestive of hemangiopericytoma than of a liposarcoma or malignant fibrous histiocytoma, two of the more common tumors of this region.