Studies of radiation carcinogenesis in rodent models have shown that chromosomal deletions affect tumor suppressor genes in mouse acute myeloid leukemia [35], lymphoma, sarcoma and mammary carcinoma in Trp53+/− mice [36–38], intestinal tumors in Apc-deficient mice [14–16, 39], medulloblastoma in Ptch1+/− mice [33, 40], renal tumors in Tsc2+/− Eker rats [34] and rat mammary cancer [41–44]. The gene discussed is PTCH1; the disease is breast cancer.