Myeloid cells, B-cells, and activated T-cells all expressprogrammed death-1 (PD-1). One indicator ofangioimmunoblastic lymphoma that points to a distinct cellof origin for the tumour is anti-PD-1. Since few B-cellsexpress PD-1, as opposed to CD10 and BCL6, anti-PD-1 maybe a more accurate and practical marker for identifyingangioimmunoblastic lymphoma. Furthermore, PD-1expression shows that angioimmunoblastic lymphoma is atumour that originates from T-cells linked with germinalcentres. This paradigm of T-cell oncogenesis, in whichparticular subtypes of T-cells may undergo neoplastictransformation and result in specific distinct histologic,immunophenotypic, and clinical subtypes of T-cellneoplasia, is further supported by the presence of PD-1 inangioimmunoblastic lymphoma.