Scientists have learned that cancer is caused by changes in genes that normally control the growth and death of cells. Certain lifestyle and environmental factors can change some normal genes into genes that allow the growth of cancer. Many gene changes that lead to cancer are the result of tobacco use, diet, exposure to ultraviolet (UV) radiation from the sun, or exposure to carcinogens (cancer-causing substances) in the workplace or in the environment.
Some gene alterations are inherited (from one or both parents). However, having an inherited gene alteration does not always mean that the person will develop cancer; it only means that the chance of getting cancer is increased. Scientists continue to examine the factors that may increase or decrease a person's chance of developing cancer.
Rarely, several generations of the same family will develop the same type of cancer at rates much higher than those that occur in the population overall. Often, the family members are passing on mutated genes that impart a higher than average risk for developing this particular cancer. By studying the genetic profiles of these affected families, researchers are learning which genes are involved in cancer's development. Kidney cancer families are a good example of this. When scientists discovered the gene changes involved in the inherited form of renal cancer, they were able to use this information to better detect and diagnose sporadic or randomly occurring new cases of this cancer type.
Only about 2 to 5 percent of cancers run in families this way.
Although being infected with certain viruses, such as the human papillomavirus (HPV), hepatitis B and C (HepB and HepC), and human immunodeficiency virus (HIV), increases the risk of some types of cancer, cancer itself is not contagious. A person cannot catch cancer from someone who has this disease. Scientists also know that an injury or bruise does not cause cancer.