Liposarcomas represent 25% of soft tissue sarcomas and can be divided into three categories:  atypical lipomatous tumour (ALT)/well-differentiated liposarcoma (WDLPS) or dedifferentiated liposarcoma (DDLPS), myxoid/round cell LPS, and pleomorphic LPS.

ALT/WDLPS account for 40-50% of all liposarcomas and typically present in the 6th decade as slow growing tumours that are often asymptomatic.   They usually arise in the retroperitoneum and total excision is unlikely and thus these tumours have a high incidence to recurrence.

DDLPS represents 15-20% and typically presents in the 6th decade of life.  The most common site of DDLPS is retroperitoneum but can include the spermatic cord, head, neck and trunk.  Unlike WDLPS, these tumours typically present as large painful masses.   Dedifferentiated areas can represent a pleomorphic sarcoma or an intermediate or high grade myxofibrosarcoma. 

These tumours have supernumerary ring chromosomes or larger marker chromosomes that are composed of 12q15 and containing the MDM2 locus and also commonly the CDK4 locus. Amplification of MDM2 results in the down-regulation of TP53 and thus decreases apoptosis and increases cell survival. 


Liposarcoma mutation detection is offered for patients with the following indications:

  • Liposarcoma
  • Atypical lipomatous tumour (ALT)
  • Well-differentiated liposarcoma (WDLPS)
  • Dedifferentiated liposarcoma (DDLPS)


  • Completed CGL Cytogenetics Solid Tumour Testing requisition form
  • FFPE Tumour specimen (see Specimen GuidelinesCytogenetics FISH FFPE test type)
    • An H&E stained slide with the tumour region circled, and the estimated % tumour content written in the Tumour Content field of the requisition.  NOTE: A minimum of 10% tumour and at least 200 nuclei is required.
    • Specimen block and/or at least one unstained slide for each probe requested.


Results are reported within fourteen days from receipt of specimen and completed requisition form.  


  • Specimens are reported as Positive for MDM2 amplification, Negative for MDM2 amplification (see method section below for MDM2 amplification calculation).
  • Almost all de-differentiated and well-differentiated liposarcomas have MDM2 amplification by FISH but can also be identified in other high grade sarcomas (e.g. malignant peripheral nerve sheath tumours, myxoid fibrosarcomas and hemangiopericytoma). 
  • MDM2 amplification by FISH is rarely seen in benign lipomas


FISH analysis is performed on the provided paraffin embedded tissue using a dual colour probe (Vysis) to MDM2 and a control probe to centromere 12. The average number of MDM2 and centromere 12 signals for all nuclei are used to calculate the ratio of MDM2 signals to CEP12 signals within a given specimen.  If the ratio is greater than 3, the sample is positive for MDM2 amplification.


  1. Weaver et al Mod Pathol (2008) PMID: 18836421
  2. Kimura et al Int J Clin Exp Pathol (2013) PMID: 23826411
  3. Coindre et al Virchows Arch (2010) PMID: 19688222