Home Education AUAUniversity Education Products & Resources Pathology for Urologists Retroperitoneum Liposarcoma


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  • 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).

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  • Histology:
    • 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.