Well-differentiated liposarcoma, light micrograph. Liposarcoma is one of the most common sarcomas of adulthood. It arises from fat in deep soft tissues of the extremities and retroperitoneum. The patients are usually in their sixth or seventh decades of life. Histologically, liposarcomas are subdivided into well-differentiated, myxoid and pleomorphic subtypes. This image shows a well-differentiated liposarcoma with a lipoma-like appearance. It has also been referred to as atypical lipomatous tumour. It consists of mature fat with a variable number of spindled cells containing atypical hyperchromatic nuclei. One such cell in seen in the centre of this image. Dense areas of fibrosis are also usually present. Well-differentiated liposarcomas contain giant marker and ring chromosomes containing amplified sequences of several genes, including MDM2 and CDK4. MDM2 gene amplification by fluorescence in-situ hybridization is a sensitive and specific means of diagnosing well-differentiated liposarcoma. Magnification: x400.