To identify diagnostic tools distinguishing AOSD and AITL, we performed IHC for CXCL10, CXCL13, CXCR3, S100A8/A9, PD-1 and CD21, which are particularly useful markers for the diagnosis of AITL22. The gene discussed is CXCL13; the disease is angioimmunoblastic T-cell lymphoma.