Genome-wide association studies identified HLA and non-HLA susceptibility genes in SS, and non-HLA genes include STAT4, C-X-C chemokine receptor (CXCR) 5 (CXCR5), TNIP1, GTF21, TNFAIP3, PTPN22, IRF5, IL21A, BLK, BLK-FAM167A, BAFF, and EBF. Here, BLK is linked to synovial sarcoma.