PDCD1 and angioimmunoblastic T-cell lymphoma: This is further characterized by TFH lymphocyte derivation and the presence of FYN, CXCL13, PD1 and vascular endothelial growth factor (VEGF) expression in recognized AITL, along with descriptions of a proliferation of follicular dendritic cells and malignant TFH cells within close proximity high endothelial venules in pathological samples (12, 49, 50).