Low-grade liposarcoma with osteosarcomatous dedifferentiation: radiological and histological features

We describe the radiological and pathological findings of a rare case of a low-grade liposarcoma associated with a high-grade osteosarcomatous component in a 78-year-old woman. Pre-operative imaging demonstrated a well-encapsulated homogeneous fatty tumour in the right buttock deep to the gluteal musculature. Centrally within the fatty tumour a region of increased soft tissue attenuation on CT and heterogeneous high signal on fat-saturated T2-weighted MRI was seen with amorphous calcification/ossification. Histological assessment revealed a low-grade liposarcoma containing an area of dedifferentiation that resembled an osteosarcoma. We describe the radiological-pathological findings in this rarely reported clinical entity and discuss the differential diagnosis of calcification within lipomatous tumours. (orig.)