Myxoid pleomorphic liposarcoma

Dr Joachim Feger et al.

Myxoid pleomorphic liposarcomas are extremely rare aggressive malignant neoplasms arising from adipocytic tissues characterized by a mixture of pleomorphic and myxoid features and the absence of genetic fusions and amplifications seen of well-differentiated liposarcoma and other lines of differentiation.

Myxoid pleomorphic sarcomas are extremely rare and affect children and young adults up to the age of 30 years on most occasions. Women are more frequently afflicted 1,2.

There have been associations of myxoid pleomorphic liposarcoma and Li Fraumeni syndrome 3-5.

The most common presentation is that of a large soft tissue mass 1.  

Myxoid pleomorphic liposarcomas are highly malignant neoplasms characterized by an admixture of myxoid liposarcoma-like zones and densely pleomorphic cellular areas with pleomorphic lipoblasts as seen in pleomorphic liposarcoma. Since 2020 they are considered a separate entity in the WHO classification of soft tissue tumors 1,2.

The most frequent site of involvement by myxoid pleomorphic liposarcoma is the mediastinum. There are also reports of the thigh, head and neck, perineum abdomen and back 1.

Myxoid pleomorphic liposarcomas are not encapsulated and are characterized by ill-defined margins 1.

The microscopic appearance of myxoid pleomorphic liposarcomas is characterized by a mixture of myxoid and pleomorphic features and includes the following 1,2:

  • infiltrative margins
  • abundant myxoid matrix with plexiform vascular patterns
  • scattered lipoblasts
  • pleomorphic spindle cells
  • pleomorphic lipoblasts
  • increased mitotic activity and atypical mitosis
  • occasional necrosis

Myxoid pleomorphic liposarcomas do not feature specific immunotypes 1.

Genetically there are no FUS/ESWR1-DDIT3 fusions like in myxoid liposarcoma and no amplification involving the MDM2 nuclear gene as seen in well-differentiated or dedifferentiated liposarcoma 1.

Descriptions about imaging characteristics dedicated to myxoid pleomorphic liposarcomas are scarce. They probably look like heterogeneous soft tissue masses with myxoid components which are characterized by high water content.

The radiological report should include a description of the following:

  • form, location and size
  • tumor margins
  • amount of solid and fatty components
  • relation to other organs structures

Myxoid pleomorphic liposarcomas are characterized by a high local recurrence, distant metastases and a poor survival rate 1.

Conditions which can mimic the clinical or radiological presentation of myxoid pleomorphic sarcoma are any fast-growing soft tissue tumors and include 1:

Article information

rID: 85126
Tag: cases
Synonyms or Alternate Spellings:
  • Myxoid pleomorphic liposarcomas

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