We reviewed 31 cases of TdT‐positive LBCL and B‐ALL/LBL, and their final diagnosis included 19 diffuse large/high‐grade BCLs with MYC and BCL2 rearrangements (five DLBCL‐MYC/BCL2, 14 HGBCL‐MYC/BCL2), three DLBCL not otherwise specified (NOS), three HGBCL‐NOS, four B‐ALL/LBL, and two unclassifiable cases. This evidence concerns the gene DNTT and acute lymphoblastic leukemia.