[31] Detection of MDM2/CDK4 Amplification in Lipomatous Soft Tissue Tumors from Formalin-Fixed, Paraffin-Embedded Tissue: Comparison of Multiplex Ligation-Dependent Probe Amplification (MLPA) and Fluorescence In Situ Hybridization (FISH).

David Creytens, Sung Ah Schoondermark-Stolk, Ernst-Jan Speel, Joost van Gorp, Patrick Pauwels. University Hospital Antwerp, Antwerp, Belgium; Diakonessen Hospital Utrecht, Utrecht, Netherlands; University Hospital Maastricht, Netherlands

Background: Several recent publications show that atypical lipomatous tumors (ALT) /well-differentiated liposarcomas (WDLPS) and dedifferentiated liposarcomas (DDLPS) share common molecular cytogenetic abnormalities, such as the presence of ring or large-marker chromosome containing amplification of the 12q14-15 region, including the MDM2 and CDK4 genes. Recently, a new method has been described for the measurement of gene copy number: MLPA.
Design: In this study the detection of MDM2 and CDK4 amplification was evaluated in lipomatous soft tissue tumors using MLPA, a PCR based technique, in comparison with FISH on a series of 85 formalin fixed paraffin embedded lipomatous tumors (27 benign adipose tumors, 36 ALT/WDLPS, 18 DDLPS, and 4 pleiomorphic liposarcomas (PLPS) to identify amplification of MDM2 and CDK4 genes and compared the results with those obtained with FISH and MDM2/CDK4 immunohistochemistry.
Results: No amplification was seen in the benign adipose tumors and PLPS. MDM2 and CDK4 immunoexpression was seen in 4 and 2 benign adipose tumors respectively. Amplification was detected in 16 and 20 of the 32 ALT/WDLPS by MLPA and FISH respectively. In 2 of the MDM2 amplified cases there was no amplification of CDK4. MDM2 and CDK4 immunoexpression was seen in 32 and 30 ALT/WDLPS respectively. 4 cases of a ALT/WDLPS with a low amplification level (ratio ranging between 2 and 2,3) detected by FISH were undetected by MLPA. In 12 of the 16 DDLPS amplification was detected by MLPA and FISH. MDM2 and CDK4 immunoexpression was seen in 16 and 15 DDLPS respectively.
Conclusions: The concordance between MLPA and FISH was 100% in cases of a high level of amplification of MDM2 and CDK4. A few cases of a ALT/WDLS with a low amplification level detected by FISH were undetected by MLPA. Therefore, MLPA proves to be an appropriate technique for screening MDM2/CDK4 amplification in lipomatous soft tissue tumors, which provides an alternative or additional test to determine MDM2 and CDK4 amplification in liposarcomas. Surprisingly was that 12 of 32 cases of ALT/WDLS showed no MDM2 and CDK4 amplification by FISH and MLPA. All these 12 cases were relatively small and all subcutaneous. These cases were revised and are morphologically and immunohistochemically not different from ALT with MDM2/CDK4 amplification.
Category: Bone & Soft Tissue

Monday, February 28, 2011 1:00 PM

Poster Session II # 19, Monday Afternoon

 

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