MDM2, CDK4 and P16 detectors contribution to liposarcoma diagnosis

Soft tissue (ST) sarcomas constitute only 1% of all adult cancers with more than 50 histological subtypes. Liposarcoma (Lisa) is the most prevalent subtype of ST sarcomas and forms 15% of all sarcomas. Although the appearance of lipoblasts in the histopathological analysis is gold standard in the determination of liposarcoma, it might not always be possible to recognize the presence of lipoblast at the histopathological level in dedifferentiated liposarcoma (DDLS) and well-differentiated liposarcoma (IDLS). Molecular approaches such as fluorescence in situ hybridization (FISH) and PCR are the diagnostic approaches for the detection of cytogenetic diversity in tumors in recent years. In atypical lipomatous tumor/well differentiated LiSa ring chromosomes, chromosome forms showing giant forms or different structural anomalies, as well as amplifications in region 12q13-15 encoding MDM2, CDK4, HMGA2 and CHOP genes have been identified at molecular studies. It is stated that MDM2 amplifications are detected in nearly all cases and CDK4 in 90% of cases. Although the p16 gene, whose loss or mutation was detected in a large number of tumors, is not fully understood at LiSa, it has recently been shown that p16 was expressed in ALT/IDLS, but not in the majority of lipomas. The immunohistochemical examination according to the molecular methods described above is additionally favored because of its rapid and easy application and low cost. There are several studies in the literature investigating the contribution of MDM2, CDK4 and p16 markers to liposarcoma diagnosis immunohistochemically. In our research, 57 cases diagnosed as liposarcoma in Ege University Faculty of Medicine Pathology Department within 2008-2018 years, 28 cases diagnosed as benign fat tissue tumors such as lipoma, spindle cell lipoma and 10 cases including other pleomorphic sarcomas were investigated. The purpose of this study was to study the expression of MDM2, CDK4 and p16 protein by immunohistochemical methods in 95 patients. The contribution of immunohistochemical markers to the diagnosis of liposarcoma as well as the relationship between clinicopathological data such as age, tumor size, tumor grade, and tumor location was compared. Twenty-eight (29.4%) benign lipomatous tumors, 22 (23.15%) IDLS, 21 (22.10%) DDLS, 6 (6.31%) myxoid liposarcomas (MLS) and 95 (95%) of the 95 cases have been covered in our research. Eight (8.42%) cases were pleomorphic liposarcoma (PLS) and 10 (10.52%) were undifferantiated pleomorphic sarcoma (UPS). Fifty-five (57.9%) patients were male and 40 (42.1%) were female. Male:Female ratio was 1.37. Mean age of the well-differentiated LiSa cases was 65±11.3 years, 63±12.1 in the DDLS group, and 6.5±16 in the pleomorphic sarcoma group. Tumor localization revealed the most common tumor type was DDLS in the retroperitoneum and abdomen. In our study, the mean tumor size was 13.7±9.1 cm (2-47 cm). In DDLS (median tumor size 20±10.3 cm), tumor size was statistically higher than other tumor groups (p=0.001). 57.1% of dedifferentiated Lisa cases were grade II, 42.9% were grade III, half of MLS was grade II and grade III, all PLS cases were grade III and 10% of UPS group were grade II, 90% was in grade III. Our demographic findings were compatible with the literature. MDM2 was observed in 68.2% (n: 15/22) of ALT/IDLS; in 90.5% (n: 19/21) of DDLS and in 10% (n: 1/10) of UPS as positive. No staining was observed in lipoma, MLS and PLS cases. MDM2 had a sensitivity of 79%, a specificity of 98%, positive predictive value (PPD) of 97% and negative predictive value (NPD) of 85% in the diagnosis of ALT/IDLS and DDLS. CDK4 showed nuclear immunoreactivity in 19/22 (86.4%) of ALT/IDLS cases and in 15/21 (71.4%) of DDLS cases, and in six (21.4%) of benign lipomatous tumors, while MLS, PLS and no staining were observed in any of the UPSs. Sensitivity specificity, positive predictive value (PPD), and negative predictive value (NPD) of CDK4 in the differential diagnosis of lipomatous tumors was calculated as %79, %92, %89, and %83, respectively. p16 stained in 86.4% (n: 19/22) of ALT/WDLS cases, 71.4% (15/21) of DDLS cases, two (7.1%) benign lipomatous tumors and one PLS (12.5%) and one UPS (10%) case, while staining was not observed in MLS cases. The sensitivity and specificity values of p16 for ALT/WDLS and DDLS were 77% and 92%, and PPD and NPD was 89% and 83%, respectively. MDM2, CDK4 and p16 staining rates in our study were consistent with the literature data. In conclusion, it is observed that MDM2, CDK4, and p16 immunohistochemical markers are reliable screening tests for differential diagnosis of ALT/WDLS and DDLS. In the scope of our study, we noticed the diagnostic sensitivity as 58%; the specificity and PPD as 100%, when three IHC markers applied together. Similar results in different binary combinations were obtained. Multiple immunohistochemical markers can be used by the differential diagnosis of lipomatous tumors, due to immunohistochemical staining of rare non-tumoral cells such as macrophages or some benign lipomatous tumors and a few numbers of other sarcomas. However, if the research be concluded by only a single determinant, it should be kept in mind that CDK4 and p16 may exhibit nuclear staining as well as cytoplasmic staining, mainly in ALT/WDLS cases and evaluation difficulties may be preferred and MDM2 should be favored.