Is cancer contagious?

Not in the normal sense of contagious. You don't spread  cancer by sneezing ,coughing or kissing. But some viral diseases predispose patients to cancer. Hepatitis predisposes patients to liver cancer. Papilloma virus infection of the unterine cervix, which is sexually transmitted, predisposes patients to cervical cancer. Both of these cancers can be prevented by vaccines. And patients infected with HIV, who have a depressed immune system, are predisposed to several cancers.
Cancer is indirectly contagious. Some cancers can spread from person to person through genetic means - that is, through inheritance. It does not spread through direct contact from hugging, kissing or sex. There are many other mechanisms that can result in the formation of cancer such as those mentioned by Dr. Oz & Dr. DeVita (HPV, HIV, Hepatitis B,C etc.) Scientist are learning more about circulating tumor cells and cancer stem cells which is an unknown problem in the future if they are ever found in the U.S. blood supply. No one is screening for them currently, and blood transfusions are relatively safe for the most part. The best way to reduce your risk (outside of genetics) of acquiring cancer is to adopt a healthy lifestyle by stop smoking, and excessive alcohol use. Reduce your body fat (body mass index) and exercise plenty as we know that obesity is a risk factor for the development of several cancer types.
Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
Some cancer is caused by viruses that are contagious, like HIV. So in a way, you can catch cancer. HIV can be spread from person to person, and HIV can lead to cancer. You can't swap cancer through bloodstream, saliva, or germs, but in a roundabout way, you can pass along some of the things that could cause cancer.

Certain cancers can be contagious. In this video, Dr. Oz and his expert panel (Dr. Lee, Dr. Cass, Dr. Richardson) dispel common myths about cancer.

YOU: The Owner's Manual, Updated and Expanded Edition: An Insider's Guide to the Body that Will Make You Healthier and Younger

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YOU: The Owner's Manual, Updated and Expanded Edition: An Insider's Guide to the Body that Will Make You Healthier and Younger

Between your full-length mirror and high-school biology class, you probably think you know a lot about the human body. While it's true that we live in an age when we're as obsessed with our bodies as...

Some cancers—like cervical cancer, or liver cancer caused by hepatitis B—are caused by viruses that are contagious (that's why there are vaccines). So in a way, you can catch cancer. But you can't directly swap cancer through being in a room with or touching or hugging someone.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.