The third step is metastasis . This is the invasion of cancerous cells into nearby tissues as well as the migration of cancerous cells to other tissues via circulatory or transport systems. Substances introduced to the body can cause mutation, promotion , or both. A carcinogen which causes both is called a 'complete carcinogen'. Physical damage to tissues can cause cell proliferation.
Some mutagens can damage surrounding tissues, leading to cell proliferation.
This may also lead to cancer. Excess consumption of fat or salt, tobacco use, and alcohol consumption can raise susceptibility to chemical insult resulting in disease. Please see our Extoxnet FAQ page on Diet and Cancer. Please see The Institute for Environmental Toxicology's site on Carcinogenicity .