CXCL13 and neoplasm: Although the WHO criteria specifically state that expression of at least three Tfh markers is required for assignment of a Tfh phenotype (38, 95), we detected a high level of heterogeneity concerning six Tfh markers, which were robustly co expressed in the tumor niche, that is to say CD4, PD-1, CXCR5, ICOS, Bcl6, and CXCL13.