The genetics of cancer is a complicated story. Through widespread efforts of cancer researchers around the world, our understanding of the role of genetics in cancer has developed tremendously. It is important to understand that cancer is a multi-factorial disease, where both genetic and environmental factors contribute to risk on an individual basis. A person who inherits a cancer-risk gene does not necessarily show symptoms or ever develop cancer, but they can still pass this gene to their children. Although not all forms of cancer are inherited, studies have identified over 50 hereditary cancer syndromes with strong evidence for a genetic link.