POU5F1 and synovial sarcoma: To further examine the role of SYT-SSX1, we collected tissues from 15 patients with synovial sarcoma and 8 tissues from chronic synovitis or next to the tumor, and then detected mRNA levels of the CSC markers (Nanog, SOX-2, and OCT-4), self-renewal factors (LIF and LIFR) and proliferation index (Ki-67) using RT-PCR.