No. Even if a cancer susceptibility variant is present in a family, it does not necessarily mean that everyone who inherits the variant will develop cancer. Several factors influence whether a given person with the variant will actually develop cancer. One is the penetrance of the variant. When not all people who carry a variant go on to develop the disease associated with that variant, it is said to have incomplete or reduced penetrance. Hereditary cancer syndromes can also vary in their expressivity—that is, people who inherit the variant may vary in the extent to which they show signs and symptoms of the syndrome, including the development of associated cancers. Lifestyle factors and environmental risks can also influence disease expression.