SS18 and synovial sarcoma: Many studies have reported the prognostic impact of SS18–SSX fusion type on synovial sarcomas, but it still remains a matter of debate (Kawai et al. 1998; Ladanyi et al. 2002; Guillou et al. 2004; Skytting 2000; Nilsson et al. 1999; Hill et al. 2003; Canter et al. 2008; Panagopoulos et al. 2001; Mezzelani et al. 2001; Takenaka et al. 2008; ten Heuvel et al. 2009; Sun et al. 2009; Krieg et al. 2011; Charbonneau et al. 2013; Ren et al. 2013).