Key result
MDM2 gene amplification testing via FISH demonstrated a sensitivity of 94.7% in dedifferentiated liposarcomas and 100% in well-differentiated liposarcomas.
Why the study?
Does MDM2 gene amplification testing and immunostaining accurately diagnose ALT/WDLPS and DDLPS?
Observational (n=77)
Does MDM2 gene amplification testing and immunostaining accurately diagnose ALT/WDLPS and DDLPS?
MDM2 gene amplification testing by FISH is highly sensitive for diagnosing ALT/WDLPS and DDLPS, and MDM2/p16 INK4a immunostaining is useful for triaging cases.
MDM2 testing may aid ALT/WDLPS and DDLPS diagnosis locally; extends prior data to the subcontinent but leaves open larger validation.
Background: Liposarcomas including atypical lipomatous tumors (ALT)/well-differentiated liposarcomas (WDLPS) and dedifferentiated liposarcomas (DDLPSs) display a histomorphological spectrum with their several diagnostic mimics. Murine double minute 2(MDM2) gene amplification characterizes ALT/WDLPS and DDLPS. Presently, there is no documented study from our subcontinent on the validation of MDM2 gene testing in these tumors. Material and Methods: Twenty-eight cases, diagnosed as ALT/WDLPS ( n = 5) and DDLPSs ( n = 23), along with 10 other tumors were tested for MDM2 gene amplification, using fluorescence in situ hybridization (FISH) on tissue microarrays (TMAs). Fourteen cases, diagnosed as ALT/WDLPS and DDLPS, along with 49 other tumors were tested for MDM2 immunostaining. Twenty tumors were tested for p16 INK4a immunostaining. Results: FISH was interpretable in 25 (89.2%) cases. Among the 20 cases diagnosed as DDLPSs, 19 displayed MDM2 gene amplification. Among the 5 cases diagnosed as ALT/WDLPS, four showed MDM2 gene amplification. Finally, 19 cases were confirmed as DDLPS and 4 as ALT/WDLPS. Furthermore, 7/19 cases confirmed as DDLPS and all 4 cases as ALT/WDLPS tested for MDM2 immunostaining, displayed its diffuse immunoexpression, while a single case of DDLPS showed its focal immunostaining. None of the 49 control cases displayed diffuse MDM2 immunoexpression. ALL 16 DDLPSs and 4 cases of ALT/WDLPS displayed p16 INK4a immunostaining. The sensitivity for diffuse MDM2 immunostaining was 87.5% in cases of DDLPS, 100% in ALT/WDLPS, and specificity was 100%. The sensitivity for MDM2 gene amplification was 94.7% in cases of DDLPS and 100% in cases of ALT/WDLPS. The sensitivity for p16 INK4a was 100%. Conclusion: This constitutes the first sizable study on MDM2 testing in ALT/WDLPS and DDLPS from our subcontinent using TMAs. MDM2 gene amplification testing continues as the diagnostic gold standard for ALTs/WDLPSs and DDLPSs and is useful in cases of diagnostic dilemmas. Diffuse MDM2 (IF2 clone) and p16 INK4a immunostaining, together seem useful for triaging cases for FISH.
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Rekhi et al. (2022) conducted an observational in Liposarcomas (ALT/WDLPS and DDLPS) (n=77). MDM2 gene amplification testing via FISH and immunostaining vs. Control tumors was evaluated on Sensitivity and specificity of MDM2 gene amplification and immunostaining. MDM2 gene amplification testing via FISH demonstrated a sensitivity of 94.7% in dedifferentiated liposarcomas and 100% in well-differentiated liposarcomas.
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