Retroperitoneal malignant mesenchymoma: imaging findings in five cases

Background: To describe computed tomographic (CT), magnetic resonance (MR), ultrasonographic (US), and angiographic findings of retroperitoneal malign ant mesenchymoma with emphasis on CT findings. Methods: Five CT, four US, four angiography, and two MR studies were obtain ed in five patients with pathologically proven retroperitoneal malignant me senchymoma. Results: Tumors were larger than 10 cm (n = 4), well-cimcumscribed and hete rogeneous (n = 4), and with massive intratumorous calcifications (n = 3) on plain CT or US. Tumors showed heterogeneous enhancement on contrast-enhanc ed CT scans (n = 4) and moderate hypervascularity with heterogeneous staini ng on angiography (n = 3). Tumors were essentially hypointense on T1-weight ed MR images (n = 2) and heterogeneous hyperintense on Ta-weighted MR image s (n = 2). Plain CT showed a fat-dense structure in a tumor in one patient. Conclusions: The radiologic findings of large expansile heterogeneous masse s in the retroperitoneum, especially with massive calcifications, were cons idered to be typical of malignant. mesenchymomas.