Comparative studies on the molecular and cellular phenotypes for the NOD.Stat5bTg mice, which have a high lymphoma incidence, and the B6.Stat5bTg and NOD/B6 F1.Stat5bTg mice which have low incidence of lymphoma, shed new lights on the role of Stat5b and the NOD genetic background on lymphomagenesis. Here, STAT5B is linked to lymphoma.