In line with a B‐cell origin, Rosa26‐Lmo2 + Mb1‐Cre and Rosa26‐Lmo2 + Aid‐Cre T‐ALL also showed clonal genomic rearrangements of genes encoding VDJ regions of immunoglobulin heavy‐chain locus (Fig 5F). Here, CD79A is linked to acute lymphoblastic leukemia.