In order to characterize lymphomas arisen in the two cohorts, we performed extensive immunophenotyping of 11 EμMycPrep1+/+ and 22 EμMyc Prep1+/− mice using antibodies for markers characterising different subsets of early B cells: anti-B220, anti-IgM and anti-CD43. The gene discussed is PKNOX1; the disease is lymphoma.