[Anatomopathology, computerized tomography, and magnetic resonance correlations in soft tissue liposarcoma]

Liposarcomas are one of the most common soft tissue malignant tumors; they can be differentiated in four histologic subtypes: well-differentiated, myxoid, round cell and pleomorphic liposarcomas. The search of differential CT and MR patterns to better classify the lesions in the proper histologic subtype is justified by the different histologic features, clinical course and especially prognosis, of every lesion subtype. From 1990 to 1995, 50 liposarcoma patients were examined preoperatively with CT and MRI in our Institute of Radiology. We found 7 well-differentiated liposarcomas (14%), twenty myxoid liposarcomas (40%), ten round cell liposarcomas (20%) and, finally, 13 pleomorphic liposarcomas (26%). The thigh was the most common tumor site (60%). The following parameters were considered: lesion margins, tissue homogeneity, fat tissue ratio and the presence of calcifications. Well-differentiated liposarcomas presented well-defined and regular margins (72%), mildly heterogeneous appearance (44%) and more than 75% fat tissue (72%). Myxoid liposarcomas presented well-defined and regular margins (65%), heterogeneous appearance (65%) and less than 25% fat tissue (95%). The diagnosis of myxoid liposarcoma can be made in the presence of myxoid tissue, which has very low CT attenuation values and mildly hypointense signal on T1-weighted and progressively hyperintense signal on T2-weighted MR images. Round cell and pleomorphic liposarcomas are high-grade malignancies and they cannot be distinguished from other malignant soft tissue lesions. In these cases, the diagnosis can be made only at histology.