Because our previous findings showed the disappearance of both the eGCs and the CXCL13 expression in LSGs, the inhibitory effect of HCT‐5 and MT‐2 cells on FDC‐like cells observed herein is a novel finding that may help explain why the LSGs of HAM‐SS patients show a hypoplastic formation of eGCs compared to the LSGs of HTLV‐1‐seronegative patients with SS. Here, CXCL13 is linked to synovial sarcoma.