Updated: 5/8/2019

Liposarcoma

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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
Introduction
  • Liposarcomas are a heterogenous class of sarcomas with differentiation towards adipose tissue
    • the lipoblast (signet ring-type cell) is a hallmark of liposarcomas 
  • Epidemiology
    • liposarcomas are the second most common form of soft tissue sarcomas in adults
    • lipomas do not predispose a patient to a liposarcoma
  • Age and location
    • occur in older individuals (50-80yrs)
    • affect more males than females
    • tend to occur deep to fascia
    • more common in lower extremity than upper extremity
    • common in retroperitoneum
  • 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%
  • Prognosis
    • 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%
Classification & Grade
  • 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, such as spread to the retroperitoneum
      • 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
  • Well-differentiated liposarcoma (central/retroperitoneal) 
    • also known as atypical lipomatous tumor (extremities)
    • low grade
    • atypical lipoblasts, minimally cellular
    • fatty stroma background
    • stain for MDM2/CDK4 
    • 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
        • well-differentiated liposarcoma
      • outcomes
        • low risk of local recurrence, metastasis extremely rare
        • dedifferentiation risk of 2% in extremities and 20% in retroperitoneal lesions
    • 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
 
 

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Questions (11)
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(OBQ13.25) A 50-year-old male presents with a painless thigh mass that has been growing in size. A representative MRI sequence, gross specimen and histologic evaluation are shown in Figures A, B and C respectively. What is the most likely diagnosis and associated corresponding chromosomal translocation? Review Topic

QID: 4660
FIGURES:
1

Alveolar rhabdomyosarcoma; t(2;13)

4%

(120/2961)

2

Fibrosarcoma; t(11;22)

1%

(43/2961)

3

Pleiomorphic undifferentiated sarcoma; t(12;16)

2%

(74/2961)

4

Synovial sarcoma; t(X;18)

3%

(97/2961)

5

Myxoid liposarcoma; t(12:16)

88%

(2591/2961)

ML 1

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PREFERRED RESPONSE 5
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(OBQ06.207) A 56-year-old male presents with a mass in his thigh that has been slowly growing over the past year. Femur radiograph, sagittal T1 and T2 weighted MRI scans, and histology section taken from an open biopsy are shown in Figures A through D. What is the diagnosis? Review Topic

QID: 218
FIGURES:
1

Lipoma

2%

(16/919)

2

Synovial sarcoma

1%

(10/919)

3

Undifferentiated pleomorphic sarcoma

7%

(65/919)

4

Liposarcoma

89%

(816/919)

5

Hemangiopericytoma

1%

(11/919)

ML 1

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PREFERRED RESPONSE 4

(OBQ07.70) A 40-year-old female presents with a painless enlarging left thigh mass. Radiograph, T1, and T2 MRI images are shown in Figures A through C. Biopsy specimen is shown in Figure D. What is the most likely diagnosis? Review Topic

QID: 731
FIGURES:
1

Lipoma

1%

(22/1761)

2

Liposarcoma

88%

(1545/1761)

3

Hemangioma

0%

(7/1761)

4

Chondrosarcoma

1%

(11/1761)

5

Leiomyosarcoma

10%

(169/1761)

ML 2

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PREFERRED RESPONSE 2
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