CD4 and lymphoma: Most Eμ‐MYC/Vav‐BFL1 mice also developed pre‐B lymphomas (Fig. 5E, Table S2) but a significant number (7 of 11 mice analysed) additionally developed CD19−B220+CD4+ progenitor cell lymphomas that have been described before for Eμ‐MYC/Eμ‐BCL2 mice 29.