110 subfascial lipomatous tumors - MR and CT findings versus histopathological diagnosis and cytogenetic analysis

Purpose. To evaluate whether liposarcoma, atypical lipomatous tumors and li poma can be differentiated radiologically. Material and Methods: We have retrospectively analyzed CT and/or MR images of 110 subfascial lipomatous lesions. The amount of fat within the tumors w as visually graded from the Images as: none, 1-75%, 75-95% or 95-100%. The structure of non-fatty tumor components was compared. The images were compa red to histopathology and in 37 cases to cytogenetic findings. Results. Only 4 of 20 liposarcomas contained fat. All 4 lesions, histopatho logically diagnosed as atypical lipomatous tumors, contained fat but less t han 75% of tumor volume. All lesions with more fat than 75% of tumor volume were histologically diagnosed as lipomas. However, one-third of the karyot yped lipomas had ring chromosomes which are considered typical for atypical lipomatous tumors. Conclusion: When a tumor is composed more or less solely of fat, the diagno sis of a lipoma or atypical lipomatous tumor with a phenotype simulating a lipoma can be assumed. When the fat content is less than 75% of the tumor v olume or non-fatty nodules are found, biopsies from different tumor compone nts have to be performed to exclude malignancy. When no fat is found, imagi ng does not help in differentiating lipoma or liposarcoma from other soft t issue tumors.