At later age they develop a T cell malignancy, characterized by an abundant tumor environment including for the majority germinal center (GC) B cells and neoplastic T cells that have a T follicular helper (Tfh) phenotype (CD4+, PD1high, CXCR5+, ICOS+) equivalent to the Tfh gene signature in human AITL [16]. The gene discussed is CD4; the disease is neoplasm.