Dedifferentiated 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. De-differentiated liposarcoma arises when a well-differentiated liposarcoma progresses to a higher-grade, less well-differentiated neoplasm. The higher-grade component usually resembles a fibrosarcoma (as shown in this image) or an undifferentiated pleomorphic sarcoma. De-differentiation occurs after a latent period of several years. Magnification: x400.