Well-Differentiated, Myxoid/Round Cell, Pleomorphic, and Dedifferentiated Subtypes


Liposarcoma is the second most common soft tissue sarcoma after undifferentiated sarcoma, and is further subdivided into several distinctive subtypes. It can present as a low-grade or high-grade tumor, with prognosis corresponding to grade. While treatment always includes surgical excision, the use of adjuvant radiation and chemotherapy depends on the subtype, location, and grade.



  • Most common between ages 40 and 60 years

  • Very rare in children

  • Painless, enlarging mass


  • Most common in proximal extremities

  • Also occurs in retroperitoneum


  • Appearance varies by subtype

  • Well-differentiated liposarcoma is closest in appearance to lipoma, with predominantly high T1 signal

  • Myxoid/round cell liposarcoma has high water content, reflected as diffusely high signal on T2 MRI

  • Dedifferentiated liposarcoma demonstrates two distinct regions: a background of well-differentiated liposarcoma and a region appearing as a nonspecific soft tissue sarcoma, with a low T1 and high T2 signal, respectively


Well-Differentiated Liposarcoma

  • Well-differentiated liposarcoma is a slow-growing lipomatous tumor that never metastasizes but can recur locally, sometimes repeatedly. It is the most common variant, making up 40% to 45% of liposarcomas.

  • Despite the similarity in appearance between lipomas and well-differentiated liposarcomas, the two tumors can be distinguished with careful evaluation of the MRI imaging. In particular, only 4% to 9% of well-differentiated liposarcomas show thin septa, whereas the majority demonstrates thick septa or nodular nonlipomatous components.

  • In the retroperitoneum, any lipomatous tumor should be considered a liposarcoma. In contrast to liposarcomas in the extremity, retroperitoneal well-differentiated liposarcomas can cause significant mortality and even morbidity, due to repeated local recurrence. The rate of dedifferentiation in the retroperitoneum is approximately 20%, compared to less than 2% in the extremities.

  • CT scans of well-differentiated liposarcomas in the medial thigh ( left ) and in the retroperitoneum ( right ) appear as low-attenuation, fatty masses.

  • While the density closely approximates subcutaneous fat, nonlipomatous thick septations and nodularity differentiate both tumors from lipomas.

  • T1 MRI of a well-differentiated liposarcoma in the calf ( left ) demonstrates fatty high signal with prominent septation.

  • The fat-suppressed T2 image ( right ) accentuates the nonlipomatous component.

  • T1 postgadolinium MRI demonstrates patchy enhancement of the nonlipomatous areas ( left ).

  • A sectioned gross specimen ( right ) demonstrates predominant fatty tissue in large lobules (L) and prominent septa ( arrow ).

  • Grossly, these tumors appear similar to normal fat. Some tumors may contain areas of hemorrhage, as seen in this example ( left ).

  • Low-power histology demonstrates predominantly mature adipose tissue ( right ).

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