MCM2 and thymus lymphoma: With respect to the early lymphoma susceptibility phenotype in Mcm4Chaos3/Chaos3 Mcm2Gt/+ mice, it is unclear whether the type of tumor is dictated primarily by the particular Mcm depletion (in this case MCM2, thus resembling Mcm2IRES-CreERT2/IRES-CreERT2 animals), the genetic background, or the age of particular cancer onset (if animals die of thymic lymphoma at an early age, they will be unable to manifest later-arising mammary tumors).