<prompt> Lipoma becomes malignant commonly at which site:SubcutaneousSub-aponeuroticRetroperitonealIntermuscular  <response>: RETROPERITONEAL LIPOMA These swellings sometimes reach an immense size Retroperitoneal lipoma is often malignant liposarcoma and may increase rapidly in size A retroperitoneal lipoma sometimes undergoes myxomatous degeneration Clinical Features Swelling or indefinite abdominal pain More common in women Diagnosis Diagnosis is usually by ultrasound and CT scanning. 