The breast is located between the skin and the chest wall and consists of a set of glands and adipose tissue. Breast cancer is a potentially serious disease if not detected and treated in time. It occurs due to the uncontrolled proliferation of some mammary gland cells that transform into malignant cells and acquire the ability to separate from the tissues that created them to attack surrounding and, over time, more distant organs. In theory, all cells in the breast can lead to tumors, but in most cases the cancer originates from glandular cells (from the lobules) or from those that form the canal wall. There are several risk factors for breast cancer, some of which are said to be changeable because they can be acted upon to reduce the risk of developing cancer, while others cannot be changed. Among the invariable factors is age, as the risk of disease increases with age, so much so that most breast cancer cases involve women over the age of 50 and a family or personal history of breast cancer. Given the family history, it is estimated that between 5 and 7 percent of breast cancers are hereditary, or are associated with the presence of a mutation transmitted by parents in certain genes. Among the most well-known and studied genes are BRCA1 and BRCA2: mutations in these genes are responsible for about 50 percent of inherited forms of breast cancer.