A malignant tumor derived from primitive or embryonal lipoblastic cells. It may be composed of well-differentiated fat cells or may be dedifferentiated: myxoid (liposarcoma, myxoid), round-celled, or pleomorphic, usually in association with a rich network of capillaries. Recurrences are common and dedifferentiated liposarcomas metastasize to the lungs or serosal surfaces. (From Dorland, 27th ed; Stedman, 25th ed)