The etiology of cancer is multifactorial, involving multiple factors including heritable (genetic) and non heritable (environmental) factors. Cancer genetics is the study of genetic information to identify an individual with an increased risk of cancer, molecularly characterize malignancies, and assess response to treatment. For an increasing number of diseases, an example being breast cancer, DNA-based testing can be used to identify a specific mutation which may be cancer predisposing. Testing is informative for the individual and for family members to determine inheritance of the disease related mutation.