Atypical Lipomatous Tumor/Well Differentiated Liposarcoma

**Semantic type:** Neoplastic Process

**Definition:** A locally aggressive mesenchymal neoplasm composed either entirely or partly of an adipocytic proliferation showing at least focal nuclear atypia in both adipocytes and stromal cells. "Atypical lipomatous tumor" and "well-differentiated liposarcoma" are synonyms describing lesions that are morphologically and genetically identical. Amplification of MDM2 and/or CDK4 is almost always present. (WHO 2020)

**Synonyms:** - ALT - ALT/WDLPS - Atypical Lipoma - Atypical Lipomatous Tumor - Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma - Atypical lipoma - Liposarcoma, differentiated - Liposarcoma, well differentiated - Well Differentiated Liposarcoma - Well Differentiated Liposarcoma - Well-Differentiated Liposarcoma