Dedifferentiated liposarcoma of retroperitoneum: Spectrum of imaging findings in 15 patients

Background: Dedifferentiated liposarcoma is a high-grade nonlipogenic sarcoma that arises in the background of a preexisting well-differentiated liposarcoma. The purpose of this work is to evaluate the spectrum of radiologic appearance of retroperitoneal dedifferentiated liposarcoma with clinicopathologic features. Methods: Radiologic images and clinical histories of 15 patients with histologically verified retroperitoneal dedifferentiated liposarcoma were retrospectively studied. Patients included 11 men and 4 women, with mean age of 55.8 years (range, 36-74 years), and they underwent computed tomography (CT) (n=15) and magnetic resonance imaging (MRI) (n=5). Results: The mean size of the tumor was 22.6 cm with a range of 9.5-38 cm. Both CT and MRI showed well-circumscribed, large round, or lobulated retroperitoneal mass. The appearance of the tumor was classified as follows: Category I, nonfatty component within predominant fatty mass (n=5); Category II, focal fatty component within large nonfatty mass (n=6); Category III, well-defined fatty mass and well-defined nonfatty mass (n=1); Category IV, two masses with predominantly nonfatty component (n=3). Conclusion: Retroperitoneal dedifferentiated liposarcomas present various spectra of imaging findings. While Categories I and III may suggest dedifferentiated liposarcoma, Categories II and IV may appear as other types of liposarcoma or other malignant retroperitoneal tumor.