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A risk factor is anything that affects a person's chance of
getting a disease such as cancer. Different cancers have different risk
factors. For example, exposing skin to strong sunlight is a risk factor
for skin cancer. Smoking is a risk factor for cancers of the lung,
mouth, larynx (voice box), bladder, kidney, and several other organs.
But risk factors don't tell us everything. Having a risk
factor, or even several, does not mean that a person will get the
disease, and many people get cancer without having any known risk
factors.
Since the exact type of a cancer of unknown primary (CUP) is
not known, it is hard to identify factors that may affect risk. These
cancers are also a very diverse group, making this issue even more
complicated. But there is research that provides some information about
CUP risk factors.
Smoking is probably an important risk factor for CUP. More
than half of patients with CUP have a history of smoking. When autopsy
studies are done, many cancers of unknown primary are found to have
started in the pancreas,
lungs,
kidneys,
throat,
larynx,
or esophagus.
Smoking increases the risk for all of these cancers.
Some other cancers of unknown primary are eventually found to
have started in the stomach,
colon,
rectum, or ovaries.
Diet, nutrition, and weight are factors that have been linked to these
cancers. (For more information, see the separate American Cancer
Society documents on these cancers.)
Melanoma
(an aggressive type of skin cancer) is another source of cancer of
unknown primary. An important melanoma risk factor is exposure to
ultraviolet radiation in sunlight.
Overall, however, there are no factors that specifically
increase the risk of cancer of unknown primary. Even in people who may
have one or more of the risk factors above, it is not possible to know
for sure if these factors contributed to the cancer.
Last Medical Review: 10/28/2008 Last Revised: 10/28/2008
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