MR Imaging of Lipomatous Soft Tissue Tumor: Histopathologic Correlation

ABSTRACT

PURPOSE: The purpose of this study to access MR findings of the lipomatous soft tissue tumor based on histopathologic correlation and its predictability of the histopathologic diagnosis. MATERIALS AND METHODS: We retrospectively analyzed the MR findings and photomicrographs of 9 patients with histopathologically proven lipomatous soft tissue tumors as follows;classic lipoma(4), fibrolipoma(1), lipoblastoma(2), atypical l ipoma(1) and well-differentiated liposarcoma(1). RESULTS: All cases of lipoma showed the same signal intensities as subcutaneous fat which is composed of mature fat cells. Linear low signal intensity lesions corresponded to fibrous connective tissues within lipomas. Two cases of lipoblastoma showed heterogeneous signal intensity with areas of high signal intensity brighter than subcutaneous fat on T2WI, corresponding to myxoid matrix of cytoplasm of immature lipoblasts, and the areas of myxoid degeneration within tumors. Both atypical lipoma and liposarcoma showed heterogeneous signal intensity with ill-defined margins due to presence of lipoblasts and infiltration to adjacent muscle bundles. CONCLUSION: MR image findings were well correlated with histopathologic findings of lipomatous soft tissue tumor, especially with maturity of fat cells and the signal intensity of mesenchymal components within the tumors. MR may predict the pathologic diagnosis of lipoblastoma by presence of myxoid degeneration within Ihe tumor, but atypical lipoma and liposarcoma revealed similar MR findings.