American Urological Association - Liposarcoma
- Most common retroperitoneal sarcoma in adults.
- Clinical features: age 40-60 years, M=F; extremely rare in childhood.
- Gross: Generally large tumors (>5cm); well circumscribed yellow-white with lobulated cut surface which may appear fatty or fibrotic (image A).
- Amplified sequence of Chr 12q14-15 (amplification of MDM2 and CDK4).
- Most often are well-differentiated LPS.
- "Lipoma-like", most common, simulates lipoma except for scattered lipoblasts (immature adipocytes) with atypical hyperchromatic nuclei (image B) and adipocytes show more variability in size and shape than would be expected in a lipoma (image C) & (image D).
- Sclerosing type, scattered bizarre cells and lipoblast in collagenous stroma.
- Inflammatory type, lipoblasts, adipocytes, and inflammatory infiltrate of lymphocytes and plasma cells.
- Other types of liposarcoma such as pleomorphic, myxoid or round cells are very rare in retroperitoneum.
- Immunohistochemistry: S100+, nuclear MDM+ and CDK4+.
- Prognosis: These are low-grade tumors that never metastasize – although they can recur, may dedifferentiate (~20%), and THEN metastasize.
- Retroperitoneal LPS often recur because of difficulty for adequate surgical excision.