What Is the Number One Cause of Cancer?

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Reviewed on 10/17/2017

Ask the experts

What is the number one cause of cancer?

Doctor's Response

Cancer is actually a complex group of individual diseases, each with different causes and effects. At the core of causing cancer are changes that occur in the genetic material within cells, the DNA. These changes, or mutations, lead to abnormal, uncontrolled cell proliferation. Cancer mutations can be caused by a variety of situations and exposures. Causes of cancer include cancer-causing chemicals, called carcinogens, such as tobacco smoke, chemotherapies, asbestos, benzene, vinyl chloride, and many more, as well as environmental factors, such as ultraviolet light, pollution, and hepatitis B. For many forms of cancer, genetic inheritance plays a significant role in causing the disease because of inherited gene mutations.

For more information, read our full medical article about cancer signs, symptoms, treatment, and prognosis.

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Reviewed on 10/17/2017
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