Diagnostic criteria, biological behavior, and treatment approaches of leiomyosarcomas (LMS) may differ according to the origin of the tumor. This is important in terms of patient's management, especially in tumors located in the peritoneum and retroperitoneal sites. In our study, we aimed to demonstrate the immunophenotypic characteristics of uterine and extra-uterine LMS using a large antibody panel, and to determine whether they potentially play a role in the differences among these tumor

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... ps. Between 2006 and 2018, 29 uterine and 42 extra-uterine primary LMS were included in this study. Using tissue samples taken from the areas that best represented the tumor, an immunohistochemical study was performed on the blocks prepared by tissue micro-array method with estrogen and progesterone receptor (PR), WT-1, SMA, desmin, caldesmon, calponin, p16, p53, MDM2, CDK4, bcl-2, cyclin D1, fascin, EMMPRIN, FOXM1, c-erb-B2, c-Myc, PAX8, and CD117. Staining results of uterine and extra-uterine LMS were evaluated with these 20 antibodies. In uterine LMS compared with extra-uterine LMS, estrogen receptor (48% vs. 12%), PR (62% vs. 21%), desmin (79% vs. 50%), and EMMPRIN (69% vs. 45%) staining rate was detected higher. In extra-uterine LMS, caldesmon (88% vs. 69%), c-Myc (33% vs. 10%), and cyclin D1 (52% vs. 28%) were stained higher than uterine LMS (p < 0.05). No significant staining difference was detected with other antibodies. We concluded that estrogen receptor, PR, desmin, EMMPRIN, caldesmon, c-Myc, and cyclin D1 antibodies may help to determine primary origin of the tumor in LMS cases.