Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Risk factors of breast cancer belongs in the field of epidemiology of breast cancer. Breast cancer, like other forms of cancer, is considered to result from multiple environmental and hereditary risk factors. Although many epidemiological risk factors have been identified, the cause of any individual breast cancer is often unknowable. In other words, epidemiological research informs the patterns of breast cancer incidence across certain populations, but not in a given individual. Approximately 5% of new breast cancers are attributable to hereditary syndromes and well-established risk factors accounted for approximately 47% of cases.