In the present study, we measured the mRNA expression of TET1, 2, and 3 and IDH1 and 2 by quantitative real-time PCR (qPCR) in highly purified CD19+ B cells from a large cohort of CLL patients (n = 214) and correlated these data with clinical outcome. Here, TET1 is linked to B-cell chronic lymphocytic leukemia.