Definition
A malignant tumour consisting of both well differentiated liposarcoma and a transformed non-lipogenic component.
Dedifferentiation is much more common in retroperitoneal well differentiated liposarcoma than in those occurring in the limbs. 90% of cases are primary, 10% of instances of dedifferentiation occur in recurrences.
Imaging shows both lipomatous and non-lipomatous components.
Usually a fatty tumour with discrete solid non-fatty dedifferentiated areas.
The transition from well differentiated liposarcoma to dedifferentiated areas is usually abrupt but may be gradual. The dedifferentiated component is usually high grade, MFH-like pleomorphic sarcoma or myxofibrosarcoma. Less often the dedifferentiated areas are low grade non-lipogenic tumour. Heterologous elements include myogenic, osteosarcomatous, chondrosarcomatous and angiosarcomatous components and are present in 5-10% of cases. A meningiothelial-like concentric pattern has been described, associated with ossification.
Identifies heterologous elements.
High grade sarcomas not arising by dedifferentiation of liposarcoma.
The prognosis is better than that for other high grade sarcomas. Overall, 40% recur locally, but almost all retroperitoneal cases eventually recur. 15-20% show distant metastases. The extent of the dedifferentiated areas and the presence of heterologous elements does not affect prognosis. The prognostic significance of microscopic foci of dedifferentiation is uncertain. Dedifferentiated liposarcoma may recur as well differentiated liposarcoma.
World Health Organization Classification of Tumours, Tumours of Soft Tissues and Bone, IARC Press 2002.
This page last revised 4.2.2006.
©SMUHT/PW Bishop