Lipoma vs well-differentiated liposarcoma

Last revised by Henry Knipe on 22 Dec 2021

There a number of features that can help distinguish between lipoma and well-differentiated liposarcoma. This article relates to superficial well-differentiated liposarcomas that typically occur in the extremities, also known as atypical lipomatous tumors, and not retroperitoneal liposarcoma.

Epidemiology

Demographic factors that favor well-differentiated liposarcoma are age >60 years and male sex 1

Radiographic features

MRI

MRI can have 100% sensitivity for the diagnosis of well-differentiated liposarcomas, however, has a low positive predictive value due to overlap of imaging features with benign lipoma variants 2

Features that favor well-differentiated liposarcoma include  1-3:

  • size >10 cm 4-6
  • percentage fat <75%
  • thick or nodular (>2 mm) septa
  • nodular/globular areas
  • prominent high T2 signal foci
  • prominent enhancement
  • associated non-adipose mass
  • lower limb location
  • intramuscular location

Features that favor lipoma include 1-3:

  • size <10 cm 4-6
  • percentage fat >75%
  • no or few thin (<2 mm) septa
  • no or minimal enhancement
  • no or minimal high T2 signal foci
  • subcutaneous location

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Cases and figures

  • Case 1: low-grade liposarcoma
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  • Case 2: Neck intermuscular lipoma
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