In contrast to normal differentiation, and specific for ALCL when compared to AITL and PTCL-NOS, we identified DNA hypermethylation and repression of the T-cell-specific TFs LEF1, TCF7, GATA3, and BCL11B in our sample cohort. This evidence concerns the gene TCF7 and mature T-cell and NK-cell non-Hodgkin lymphoma.