What causes cancer?
What causes cancer?

Sometimes it seems cancer strikes for no reason. Scientists don't know yet what causes all cancers. But many causes are known. In general, scientists believe two major factors – heredity and environment – are the primary causes of most cancers.

Heredity refers to one’s family (genetic) background. Genes are instructions for building a person. We receive genes from each of our parents for eye color, hair color, and other traits. The number of genes in a single cell is huge. Some of these genes have factors that make us more likely to develop cancer. A family history of cancer may indicate a higher likelihood of an individual developing the disease. This is one reason why physicians ask so many questions about a patient’s family members and their health. By knowing the health of a patient’s family members, physicians can watch more carefully for a cancer’s warning signs and recommend appropriate cancer screening.

Certain genes called oncogenes are related to cancer. This is a very active area of research.

Environment refers to all of those outside factors that contribute to cancer. Chemicals, radiation, viruses and bacteria may cause cancer. Lifestyle and behavioral choices may cause cancer. The effects of smoking, air pollution, too much sunlight and certain foods can turn normal cells into cancer cells.

Scientists believe that a combination of genetic and environmental factors causes many cancers. The best course is to know your family medical history, understand your environmental risk factors, and take all appropriate steps recommended by a physician.

To learn more:

Cancer Causes and Risk Factors
(National Cancer Institute)
This list of cancer causes and risk factors leads to written discussions about specific issues. The list includes foods, genetics, hormones, smoking, workplace and environment, and other topics. Each discussion includes research results which can be hard to understand.

next » What are major cancer risk factors?

Written by: Nancy C. McKeehan, M.S.L.S.
Reviewed by: Jeffrey G. Schultze, M.D.
Last Modified: Thursday September 22, 2016 7:00 PM