A locally aggressive malignant neoplasm composed of mature adipocytes showing cell size variation and nuclear atypia. It is often associated with the presence of hyperchromatic multinucleated stromal cells, and varying numbers of lipoblasts. There are three histologic subtypes, sclerosing, inflammatory, and spindle cell liposarcoma. These tumors do not usually metastasize unless they undergo dedifferentiation. The disease is Monarch Disease Ontology entry MONDO_0005103 (well-differentiated liposarcoma). Also known as: ALT, WDLS, atypical lipoma, well differentiated liposarcoma, well differentiated liposarcoma of deep soft tissue.