Case Id: JSSMCRADC0066

Figure 1: Plain Radiograph of thigh

 

Figure 2: Coronal section, T2 weighted image
Figure 3: Coronal section, STIR image
Figure 4: Axial section, T2 weighted image
Figure 5: Coronal section, Post contrast image

 

Figure 1: Plain Radiograph of thigh shows a well defined radiolucent lesion
Figure 2: Coronal section, T2 weighted image shows a well defined hyperintense lesion with few internal septations
Figure 3: Coronal section, STIR image shows well defined capsule with minimal internal septations
Figure 4: Axial section, T2 weighted image a well defined hyperintense lesion with few internal septations
Figure 5: Coronal section, Post contrast image shows minimal capsular and internal septations showing enhancement
FINAL DIAGNOSIS LIPOSARCOMA OF THIGH

 

LIPOSARCOMA:

Liposarcomas are malignant tumours of fatty tissue and are the malignant counterpart to a benign lipoma. They are the second commonest type of soft tissue sarcoma.

Epidemiology

Liposarcomas are typically found in adults and are rare in children, typically between the ages of 40 and 60.

Clinical presentation

It varies accordingly to the tumour location, usually related to a lump mass when involving the subcutaneous and extremities, and a vague discomfort when intraabdominal or intrathoracic. 

Pathology

Thought to originate from mesenchymal cells, they are classified histologically into five types 1:

  • well-differentiated 
    • commonest (~50%) 
    • has the highest amount of fat content and is also known as an atypical lipoma , low grade 
  • myxoid
    • 2nd commonest
    • intermediate grade 
    • balanced chromosomal translocation t(12,16)
  • round cell / de-differentiated
    • De-differentiated liposarcoma
    • high grade, aggressive with frequent metastases
  • pleomorphic
    • least common
    • high grade, aggressive with frequent metastases
  • mixed

Location

They are usually seen in the extremities (75%), most commonly the thigh, and are less commonly seen in the retroperitoneum, groin or elsewhere

Radiographic features

CT

Liposarcomas have three CT patterns based on amount and distribution of fat in tumour:

  • solid: attenuation over +20 HU
  • mixed: areas of less than -20 HU and areas of over +20 HU
  • pseudocystic: homogenous density between –20 and +20 HU

CT findings favouring a liposarcoma over a lipoma include:

  • inhomogeneous attenuation, with evidence of significant amounts of soft-tissue within the fatty mass
  • poor definition of adjacent structures
  • evidence of infiltration or invasion of mediastinal structures
  • calcification  

MRI

MRI appearance, as with CT, varies depending on the grade and amount of fatty tissue.

Low grade lesions (atypical lipomas) are almost entirely fat signal with however thick septa, enhancement or evidence of local invasion. These features are used to distinguish these from simple lipomas .

The higher grade lesions are often devoid of macroscopic fat and have appearances similar to other sarcomas.

Treatment and prognosis

Both treatment and prognosis vary with location and grade.

Extremity liposarcomas, especially when well differentiated (atypical lipoma or atypical intramuscular lipoma) are indolent but nonetheless have a tendency to locally recur (0-69% of the time 2. The rate of recurrence is higher for deep lesions compared to superficial ones.

High grade lesions, especially those of the retroperitoneum have poor prognosis, with recurrence rates between 63-91% .

Surgical treatment is with wide local excision, which accounts at least in part for the more favorable outcome of extremity lesions.