For example, it is a marker of aggressive disease for certain subsets of T-cell non-Hodgkin's lymphomas/leukaemias, with expression of CD26 on T-lymphoblastic lymphomas/acute lymphoblastic leukaemia cells being associated with a worse outcome compared with CD26-negative tumours (Carbone et al, 1995). Here, DPP4 is linked to T-lymphoblastic lymphoma.