The evaluation of importance of new immunohistochemical markers for the diagnosis and differantial diagnosis of mesenchymal tumors

Background: Mesenchymal neoplasms have diagnostic challenges for even the most experienced pathologists. Mesenchymal tumors have more than 50 malignant and more than 100 benign subtypes. These tumors are hard to diagnose due to their rarity and their morphology. Sarcomas consititute 1% of all solid tumors found in adults. In the last years, there have been continuously new developments in the molecular genetics and immunohistochemistry markers in terms of diagnosis and differential diagnosis. The aim of this study is to re-evaluate the previously reported sarcomas in the light of new knowledge based on the 2013 WHO classification and newly found immunohistochemical markers and to determine of the importance of these new markers for the diagnosis of mesenchymal tumor. Design: A hundred and eighty three soft tissue sarcoma cases that were diagnosed at Pathology Department of Cukurova University Medical Faculty between 2000 to present were included in this study. These cases were re-evaluated based on 2013 WHO classification and new immunohistochemical markers (TLE1, MUC4, MDM2, CDK4, TFE3, STAT6) were applied as morphologic features and the changes in diagnosis were evaluated. Results: The diagnosis of 61 cases out of 183 was changed in this study. Among these cases, 20 of MFH were re-named as PS and three of MFH cases were re-named as Myxofibrosarcoma owing to the new WHO classification 2013. The diagnosis of the 38 cases were changed due to new immunohistochemical markers. The most alteration of the diagnosis of sarcoma groups were leiomyosarcoma and liposarcoma. Conclusions: New immunohistochemical markers have assumed an increasingly important role in diagnosis and differantial diagnosis of soft tissue tumors. However, the contribution of all of these markers to the diagnosis depend on careful morphologic evaluation and the choice of right markers by experienced pathologist. Key Words: Mesenchymal tumors, sarcoma, immunohistochemistry (MUC-4, TLE-1, MDM-2, CDK-4, STAT-6, TFE-3)