Figure 1.

Wt1-Igf2 mice developed tumors at 3–4 months age. Wt1-Igf2 mutant mice developed tumors with very high frequency (100%) compared to littermate controls. Palpable tumors were noted in all mutant mice (1B), but not in controls (1A), beginning at about 10 weeks of age. Tumor bearing kidneys were typically 10-fold larger in size and weight (1B) than littermate control kidneys (1A). The mutant mice showed the tumor histology (1B) with typical blastema, epithelia and stroma whereas control kidneys showed normal histology (1A) with H&E staining. Most of the mutant mice also showed splenomegaly (1B). Spleens of the tumor bearing mice were significantly larger than their litter mate controls by size (1B) and weight (1C).