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Updated: Feb 3 2023

Liposarcoma

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https://upload.orthobullets.com/topic/8068/images/MRI T1_moved.jpg
https://upload.orthobullets.com/topic/8068/images/MRI T2_moved.jpg
https://upload.orthobullets.com/topic/8068/images/myxoid liposarc.jpg
https://upload.orthobullets.com/topic/8068/images/t1 mri well-diff liposarcoma.jpg
https://upload.orthobullets.com/topic/8068/images/t2 mri well-diff liposarcoma.jpg
  • summary
    • Liposarcomas are a heterogeneous class of sarcomas with differentiation towards adipose tissue that consist of 5 different sub-types: well-differentiated, myxoid, round cell, pleomorphic, and dedifferentiated.
    • The condition is typically seen in patients 50-80 years of age who present with a slow-growing, painless mass.
    • Diagnosis is made with a biopsy showing immature lipoblasts with various cellular atypia depending on the sub-type. 
    • Treatment may be marginal excision for a well-differentiated liposarcoma. Wide surgical resection with radiation is indicated for intermediate and high-grade liposarcomas.
  • Epidemiology
    • Incidence
      • liposarcomas are the second most common form of soft tissue sarcomas in adults
    • Demographics
      • occur in older individuals (50-80yrs)
      • affect more males than females
    • Anatomic location
      • tend to occur deep to fascia
      • more common in lower extremity than upper extremity
      • common in retroperitoneum
  • Etiology
    • Pathophysiology
      • the lipoblast (signet ring-type cell) is a hallmark of liposarcomas
    • Genetics
      • well-differentiated liposarcoma - amplification (MDM2)
      • myxoid liposarcoma - translocation (12;16)
    • Malignant potential
      • metastasis risk correlates with grade/sub-type of liposarcoma
        • low grade (well-differentiated) has a metastasis rate of < 1%
        • intermediate grade (myxoid) has a metastasis rate of 10-30%
        • high grade has a metastasis rate of > 50%
  • Classification
    • Histologic types
      • liposarcoma types are related to the developmental stage of the lipoblasts from which they form
        • all are from primitive mesenchymal cells
      • types include
        • well-differentiated
          • same entity as atypical lipomatous tumor
        • myxoid
          • most common ~ 50% of all liposarcomas
        • round cell
        • pleomorphic
        • dedifferentiated
  • Imaging
    • Plain Radiographs
      • may show soft tissue calcification or ossification in well-differentiated liposarcomas
    • MRI
      • well-differentiated liposarcomas look similar to lipomas on MRI
        • bright on T1, dark on T2
        • may show differences in rate of growth, stranding, size
      • high-grade liposarcomas look similiar to other sarcomas on MRI
        • dark on T1, bright on T2
          • although high grade liposarcomas appear fibrogenic, they may have 10% fat composition, so they appear dark on T1 and bright on T2 unlike a lipoma which images iso-intense to sub-cutaneous fat on all sequences
    • CT Chest/Abd/Pelvis
      • myxoid liposarcomas have a tendency for abnormal metastasis outside of the lungs
        • therefore, histologic diagnosis of myxoid liposarcoma should be evaluated with CT chest/Abd/Pelvis
  • Histology
    • Characteristic histology
      • immature lipoblasts (signet ring-type cells)
      • mature adipocytes
    • Atypical lipomatous tumor (ALT; located in extremities)
      • referred to as well-differentiated liposarcoma (WDL) when located central/retroperitoneal - WDLs have a higher risk of local recurrence and metastatic spread compared to ALTs
      • low grade
      • atypical lipoblasts, minimally cellular
      • fatty stroma background
      • have ring chromosome 12
    • Myxoid liposarcoma
      • low to intermediate grade
      • proliferating lipoblasts upon a myxoid stroma matrix
      • signet ring lipoblasts may occur
    • Round cell liposarcoma
      • poorly differentiated liposarcoma with characteristic small round blue cells
    • Pleomorphic liposarcoma
      • high-grade pleomorphic tumor
      • giant lipoblasts with bizarre nuclei
    • Dedifferentiated liposarcoma
      • high-grade sarcoma adjacent to well-differentiated lipomatous lesion
  • Treatment
    • Operative
      • marginal resection without radiotherapy
        • indications
          • atypical lipomatous tumors (ALT)
        • outcomes
          • low risk of local recurrence, metastasis extremely rare
          • dedifferentiation risk of 2% in extremities (ALTs) and 20% in retroperitoneal lesions (well-differentiated liposarcomas)
      • wide surgical resection with adjuvant radiotherapy
        • indications
          • intermediate grade liposarcomas
          • high grade liposarcomas
        • outcomes
          • radiation decreases local recurrence
          • chemotherapy may be beneficial in selected patients
          • myxoid liposarcomas with >10% round cells have high likelihood of metastasis
  • Prognosis
    • Lipomas do not predispose a patient to a liposarcoma
    • Well-differentiated liposarcomas exhibit < 10% local recurrence rates and <1% chance of metastasis and almost complete survival
    • With appropriate treatment, intermediate and high grade liposarcomas show ~ 20% risk of local recurrence but they exhibit 5 year survival between 25 - 50%
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