• Takes origin from primitive mesenchymal cells rather than mature adipose cells


  • A fairly common malignancy of fat most common in the thigh, retroperitoneum, and inguinal regions
  • Most common in occurrence rates for soft-tissue sarcomas (20%)
  • Retroperitoneal lesions may occur simultaneously or sequentially to extremity lesions


  • 8 months to 87 years, mean 57 years, M:F = 3:2
  • Rare in subcutaneous fat and GI subserosa
  • Most common sites are thigh (25-30%) and retroperitoneum (?20%)
  • Unusual locations
  • Insidiously growing, deep-seated, ill-defined mass
  • Pain, tenderness only in 10-15%
  • Hemodynamic deteriorationin cardiac and abdominal locations reported
    • Synchronous cardiac and abdominal metastases 13 yrs after a thigh liposarcoma reported
  • Preexisting lipoma is extremely rare
  • Liposarcoma associated with multiple intramuscular lipomas reported in a 71-year-old
  • Has been reported in NF1


  • Depend largely on histological type
  • Well-delineated radiolucency to dense mass
  • May have foci of calcification and ossification (esp well differentiated)
  • Vascularity often seen on bone scan
  • CT may show a low density mass with an area of higher density
    • Myxoid liposarcoma may show a homogenous density between -40 to +30 Hounsfield units
  • MRI shows inhomogeneic regions, some isointense with fat
    • Intermediate T1 signal, bright on T2
  • A liposarcoma of the pectoral muscle has been reported initially detected at mammography (heterogeneous without discrete margins) in a 76 yr-old man with painless gynecomastia


  • Usually well encapsulated and distinctly lobulated (lobules can become separated)
  • Can be the largest of neoplasms, esp in the retroperitoneal location


  • Histological classification of liposarcoma
  • AFIP
    • Well-differentiated liposarcoma (atypical lipoma)
    • Lipoma-like: scattered lipoblasts
    • Sclerosing: inguinal prevalence
    • Inflammatory: prominent inflammatory component
    • Dedifferentiated: well and poorly differentiated together
    • Myxoid liposarcoma (40-50%):lipoblasts, capillaries, myxoid matrix
    • Round cell liposarcoma: tends more to metastasize
    • Pleomorphic liposarcoma: bizarre cells
  • Evans
    • Myxoid
    • Well-differentiated
    • Dedifferentiated
    • Pleomorphic
    • Well-differentiated with a pleomorphic component
  • Lipoblasts the characteristic cell
  • Vacuolated tumor cell with single vacuole and eccentric nucleus or multiple vacuoles and a central nucleus; "signet ring" cell
  • Vacuoles within the cell contain fat (+ oil red O)
  • Cytogenetic studies
    • t(12;16),(q13;p11) (in tumor lipoblasts)
    • Other abnormalities reported include trisomy 8
  • Molecular
    • Chromosome 12 amplificationin well-differentiated and dedifferentiated liposarcomas
      • MDM2 gene
      • CDK4 gene
        • ~10% do not amplify CDK4
        • Alteration in CDKN2A/CDKN2B/CDK4/CCND1 pathwaydemonstrable
          • Array-CGH
          • Real-time genomic PCR
          • Gene expression array
          • Real-time RT-PCR
        • Chromosome 1q21-1q23 is preferential partner of chromosome 12 amplicon in tumors with amplification/overexpression CDK4
    • Over 40 microRNA expression alterations reporteddysregulated in dedifferentiated liposarcomas
      • Upregulated microRNAs
        • miR-21
        • miR-26a
      • Downregulated microRNAs
        • miR-143
          • Restoring miR-143 expression:
            • Inhibited proliferation
            • Induced apoptosis
            • Decreased expression of BCL2
            • Decreased expression of topoisomerase 2A
            • Decreased expression of protein regulator of cytokinesis (PRC1)
            • Decreased expression of polo-like kinase 1 (PLK1)
              • Tx with a PLK1 inhibitor potently induced G(2)-M growth arrest and apoptosis
        • miR-145


  • If lipoblasts are seen, the dx is made
  • Lipid stains are positive in mesenchymal or epithelial neoplasms
  • Myxoid chondrosarcoma and chordoma
  • Vacuolated forms of lymphoma ("signet-ring" lymphoma)
  • Rarely meningioma, malignant melanoma
  • Intramuscular myxoma, myxoid MFH


  • Wide resection, long course in some low grade lesions
  • Lung metastases (most common) as well as viscera; check retroperitoneum (extrapulmonary metastases, esp with myxoid variant)
  • +/- XRT; preoperative + postoperative boost in higher grade lesions
    • XRT effective in preventing LR but not reported to impact survival
  • Mediastinal and bone metastases have been reported
  • Prognosis
    • 5-yr survivals (with appropriate tx)
    • 74% overall 5-yr survival, all subtypes
    • 80% myxoid liposarcoma, LR <10% with resection and XRT
    • Oral and maxillofacial region
      • Tumor size > 3.6 cm
      • Histopathologic subtype
  • Chemotx trials for lesions >8cm in diameter






    •  Any grade or histological type may be found in this location
    • Giant (50 cm and 52 kg) liposarcoma of the retroperitoneal spermatic cord reported 
    • Tumors in this location may become huge and simulate pregnancy


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