In our case, immunohistochemistry confirmed the diagnosis of monophasic synovial sarcoma, with the tumor cells being non-reactive for S-100, Smooth Muscle Actin (SMA), and neurofilament, but positive for TLE1, BCL2, and CD99, which are indicative of this type of sarcoma [12]. This evidence concerns the gene TLE1 and synovial sarcoma.