Can definitive type determination be made in spindle cell sarcomas by immunohistochemistry and cytogenetics?

Soft tissue tumors are a heterogeneous group of tumors that are difficult to distinguish from reactive process/neopasia, are rare, consist of many subgroups, do not resemble each other in their natural course, biology and treatment responses, and challenge the pathologist in daily routine. It is natural for soft tissue sarcomas to change in classification with new genetic studies and to define new entities. Sarcomas constitute 1% of all solid tumors in adults. In this study, it was aimed to reevaluate sarcomas with spindle morphology, which cannot be definitively diagnosed, using immunohistochemical markers and cytogenetic tests according to the WHO 2019 classification, and to investigate the contribution of these markers to the diagnosis. 90 patients who were diagnosed with spindle cell mesenchymal tumor in Dicle University Faculty of Medicine, Department of Pathology between 2010-2021 and whose definite type could not be determined were re-evaluated. In addition, the immunohistochemical methods applied at the time of diagnosis were re-examined with new immunohistochemical markers (MUC-4, STAT6, TLE1, INI-1, Beta catenin) and molecular studies (SS18 translocation, MDM2 amplification) applied according to their morphology and diagnostic changes were evaluated.,In this study, a definitive diagnosis was given to all 90 cases. The greatest contribution to diagnosis came from the immunohistochemical study. Immunohistochemical markers and molecular methods have an extremely important role in the diagnosis of soft tissue tumors. In addition, the correct interpretation of the study results of these markers is also very important. However, the contribution of these determinants to the diagnosis is possible with the selection of the appropriate ones, by performing a morphological evaluation by an experienced pathologist, accompanied by the detailed history and clinical findings of the case. Keywords: Spindle cell mesenchymal tumor, sarcoma, IHC (MUC-4, TLE-1, STAT-6, INI-1, Beta catenin), FISH, SS18 translocation, MDM2 amplification