The differential diagnosis of TdT‐positive DLBCL/HGBCL and B‐ALL/LBL may pose profound problems due to the overlapping features of these two diagnostic families/entities especially when MYC rearrangements are encountered in a CD34‐negative aggressive B‐cell neoplasm in an adolescent or a young adult patient. The gene discussed is MYC; the disease is B-cell neoplasm.