DPP4 and mycosis fungoides: B-chronic lymphocytic leukaemia cells have high levels of CD26 protein expression and mRNA transcripts (Bauvois et al, 1999); whereas the more aggressive T-cell malignancies, such as T-cell acute lymphoblastic leukaemia or T-cell CD30+ anaplastic large-cell lymphoma, express higher CD26 level as compared to the more indolent T-cell diseases like mycosis fungoides (Carbone et al, 1995; Jones et al, 2001).