Based on our previous work on BRCA1 tumors and the current study on CHEK2 tumors we postulate a model in which breast tumors with a defect in an essential gene such as BRCA1 or BRCA2, result in copy number profiles that reflect both the tumor subtype and specific surviving factors while breast tumors with a defect in a non-essential gene such as CHEK2, result in copy number profiles that largely reflect the tumor subtype. The gene discussed is CHEK2; the disease is breast neoplasm.