Malignant T cells and myeloid cells isolated from the same mouse displayed different karyotypes. Lymphoma T cells and malignant myeloid cells were isolated from the same animal that received a transplant of purified HSCs expressing oncogenic Kras from its endogenous locus and that developed both T-cell lymphoma and JMML (Table 1). Mouse chromosomal G-banding analysis was performed on these cells (“Methods”). A total of 18 thymic lymphoma cells were analyzed; all displayed the same karyotype. A representative image of a thymic lymphoma cell (A) showed trisomy chromosomes 14 and 15 (indicated by →) as well as gain of a fused mysterious chromosome (indicated by → labeled with marker). A total of 20 myeloid cells were analyzed; all showed apparently normal karyotype (B).