Septum-like structures in lipoma and liposarcoma: MR imaging and pathologic correlation

Objective. To-investigate the septum-like structures in predominantly lipomatous tumors, by correlating fat-suppressed MR images with histopathologic findings. Design and patients. The MR findings of three cases of well-differentiated liposarcoma (atypical lipoma), one case of lipoma-like component of dedifferentiated liposarcoma. and nine cases of lipoma were analyzed. T1-, T2-, and fat-suppressed T1- weighted images after Gd-DTPA administration were obtained. Surgical specimens from five patients (four with liposarcoma and one with lipoma) were also scanned with a MR unit, and compared with the pathologic findings. Results and conclusions. Enhancement features of lipoma and liposarcoma were well visualized on fat-suppressed T1-weighted images after Gd-DTPA administration. The septum-like structures of liposarcoma are thick and enhanced considerably, while septa of lipoma are thin and enhanced only slightly. Pathologically, the septum-like structures of Liposarcoma contained muscle fibers and the septa of lipoma represented fibrous capsule, Identification of well-enhanced septa in a predominantly lipomatous tumor helps to differentiate malignant tumors horn lipomas. As the septum-like structures of liposarcoma contain a skeletal muscle component the tumor might need more extensive surgical procedures including resection of adjacent muscles.