Monarch Disease Ontology term MONDO_0006097 (atypical lipomatous tumor) is an intermediate, locally aggressive lipomatous neoplasm. Microscopically, the adipose tissue contains large and pleomorphic lipoblasts, and is dissected by fibrous septa containing spindle cells. It requires a wide local excision, may recur locally, but never metastasizes. Also known as: ALT, Atypical lipoma, lipoma-like liposarcoma, liposarcoma, well differentiated (morphologic abnormality), superficial well differentiated liposarcoma, well differentiated liposarcoma of superficial soft tissue.