MYXOID LIPOSARCOMA - MAGNETIC-RESONANCE-IMAGING APPEARANCES

Purpose. Myxoid liposarcoma is the most common type of liposarcoma (approximately 40 to 50% of ail liposarcomas). The main tissue component is a myxoid matrix present primarily in extracellular compartments; proliferating lipoblasts account for less 10% of the tumor: MRI appearances are not typical for lipomatous tumor. Nevertheless histological features may permit understanding MRI findings and identifying patients with myxoid liposarcoma. Materials and methods. Clinical history and radiologic images of 7 patients with histologically verified myxoid liposarcoma were retrospectively studied. In all patients the tumor presented in a lower extremity as a painless, slowly growing mass. MR images were available for review in all cases (T1- and T2-weighted images); in addition fat-suppression before and after gadolinium enhancement were assessed with T1-weighted sequences. Results. MRI examination revealed an ''encapsulated'' tumor, non infiltrating and septated. On T1-weighted sequences all the lesions show lacy, amorphous and linear foci of high signal within a low signal mass: these foci represent small areas of fat within the predominantly low signal of the tumor due to the predominance of a myxoid matrix. The high sensitivity of MRI demonstrates the presence of small areas of high signal and fat-suppression technique is valuable for characterizing soft-tissue tumors: suppression of high signal intensity on fat-saturated TI-weighted images indicates the presence of fatty tissue components. Conclusion. Clinical correlation with MRI appearances on T1-weighted sequences (in addition to fat-suppression technique) may suggest the possibility of myxoid liposarcoma.