Overexpression and amplification of Murine double minute 2 as a diagnostic tool in large lipomatous tumor and its correlation with Ki67 proliferation index: An institutional experience

Context: Well-differentiated liposarcoma (WDLPS) is the most common type of liposarcoma and sometimes can be difficult to distinguish from large lipoma due to the similar morphology. Aims: This study proposed to evaluate the expression and amplification of Murine double minute 2 (MDM2) gene and determine its correlation with Ki67 proliferation index. Settings and Design: This study used cross-sectional design. Materials and Methods: This study enrolled 37 cases of lipomatous tumors with >5 cm in size. Eighteen cases of WDLPS and 19 cases of lipoma were stained for MDM2 and Ki67 immunohistochemistry, followed by MDM2 in situ hybridization in 12 selected cases. Statistical Analysis Used: MDM2 overexpression and amplification status for both groups were compared using Chi-square test, with the alternative of Fisher's exact test. Correlation test between MDM2 overexpression and clinical characteristics with the Ki67 proliferation index were performed using Pearson's test with the alternative of Spearman's rho test. Results: MDM2 overexpression was detected in all WDLPS cases and in 3 (16%) of lipoma cases with significance difference (P = 0.000), whereas MDM2 amplification was found in all WDLPS and in 1 of lipoma cases (P = 0.200). There was a strong correlation between MDM2 overexpression and higher Ki67 proliferation index (r = 0.645, P = 0.000). Conclusion: Evaluation of MDM2 overexpression can be used as a useful adjunct to differentiate WDLPS from large lipoma and seems to be related with Ki67 proliferation index.