Although MDM2 amplification is widely accepted as a marker for the diagnosis of DDLS in the internal trunk, even without associated well-differentiated liposarcoma (WDLS) component, it is still controversial whether MDM2-amplified undifferentiated sarcoma at the peripheral site (including the truncal wall) should always be classified as DDLS in the absence of WDLS. The gene discussed is MDM2; the disease is dedifferentiated liposarcoma.