(a) Schematic of generation of neurofibroma mice breeding with or without Atm heterozygosity. (b) Volumetric measurements of MRI scans of mice at 4 months of age. (n=6 Nf1 fl/fl; DhhCre, n=6 Atm+/−; Nf1 fl/fl; DhhCre). Tumor volume was increased in Atm+/−; Nf1 fl/fl; DhhCre mice. Un-paired t-test, *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001 (c) Representative images of gross dissections of spinal cords attached to peripheral nerves and tumors from mice at 7 months of age. (d, e) Statistical analysis (n=8 mice, Nf1 fl/fl; DhhCre, n=11 mice, Atm+/−; Nf1 fl/fl; DhhCre, at 7 months of age. (d) Tumor number/mouse, unpaired t-test. (e)Tumor diameter: Nf1 fl/fl; DhhCre mouse total of 30 tumors and Atm+/−; Nf1 fl/fl; DhhCre total of 102 tumors, unpaired t-test.