MYXOID LIPOSARCOMA - MAGNETIC-RESONANCE-I MAGING APPEARANCES

Purpose. Myxoid liposarcoma is the most common type of liposarcoma (ap proximately 40 to 50% of ail liposarcomas). The main tissue component is a myxoid matrix present primarily in extracellular compartments; pr oliferating lipoblasts account for less 10% of the tumor: MRI appearan ces are not typical for lipomatous tumor. Nevertheless histological fe atures may permit understanding MRI findings and identifying patients with myxoid liposarcoma. Materials and methods. Clinical history and r adiologic images of 7 patients with histologically verified myxoid lip osarcoma were retrospectively studied. In all patients the tumor prese nted in a lower extremity as a painless, slowly growing mass. MR image s were available for review in all cases (T1- and T2-weighted images); in addition fat-suppression before and after gadolinium enhancement w ere assessed with T1-weighted sequences. Results. MRI examination reve aled an ''encapsulated'' tumor, non infiltrating and septated. On T1-w eighted sequences all the lesions show lacy, amorphous and linear foci of high signal within a low signal mass: these foci represent small a reas of fat within the predominantly low signal of the tumor due to th e predominance of a myxoid matrix. The high sensitivity of MRI demonst rates the presence of small areas of high signal and fat-suppression t echnique is valuable for characterizing soft-tissue tumors: suppressio n of high signal intensity on fat-saturated TI-weighted images indicat es the presence of fatty tissue components. Conclusion. Clinical corre lation with MRI appearances on T1-weighted sequences (in addition to f at-suppression technique) may suggest the possibility of myxoid liposa rcoma.