TET2is involved in a variety of hematopoietic malignancies, mainly in myeloid malignancies. Most mutations ofTET2have been identified in myeloid disorders, but some have also recently been described in mature lymphoid neoplasms. In contrast to the large amount of data about mutations ofTET2, some data are available for gene expression. Moreover, the role of TET2 in chronic lymphocytic leukemia (CLL) is unknown. This study analyzes bothTET2expression and mutations in 48 CLL patients.TET2expression was analyzed by exon arrays and quantitative real-time polymerase chain reaction (qRT-PCR). Next-generation sequencing (NGS) technology was applied to investigate the presence ofTET2variations. Overexpression ofTET2was observed in B-cell lymphocytes from CLL patients compared with healthy donors (P= 0.004). In addition, in CLL patients, an overexpression ofTET2was also observed in the clonal B cells compared with the nontumoral cells (P= 0.002). However, no novel mutations were observed. Therefore, overexpression ofTET2in CLL seems to be unrelated to the presence of genomicTET2variations.