A risk factor is anything that may increase your chance of having a disease. Risk factors for a certain type of cancer might include smoking, diet, family history, or many other things. The exact cause of someone's cancer may not be known. But risk factors can make it more likely for a person to have cancer.

Things you should know about risk factors for cancer:

• Risk factors can increase a person's risk, but they do not always cause the disease.
• Some people with one or more risk factors never develop cancer. Other people with cancer have no risk factors.
• Some risk factors are very well known. But there's ongoing research about risk factors for many types of cancer.

Some risk factors, such as family history and age, may not be in your control. But others, like diet, sun exposure, weight, and tobacco and nicotine use, are things that you can change. Knowing cancer risk factors can help you make choices that might help lower your overall cancer risk.

Almost any type of primary cancer can be a source for cancer of unknown primary (CUP) origin. So, the risk factors for most types of cancers are also risk factors for CUP. Because doctors don't know the why, how, or where of cancer of unknown primary origin (CUP), it's hard to identify specific risk factors for it. Still, there are certain kinds of cancer that are more likely linked to CUP.

For instance, experts know that cigarette smoking and using other tobacco or nicotine products are known risk factors for many kinds of cancer that could lead to CUP. This includes chewing tobacco, vaping, and cigar smoking.

Age increases the risk for CUP. The incidence of CUP is highest in people between ages 60 and 75.

Certain diets and being at a higher weight or having obesity have been linked to cancers of the stomach, colon, or rectum. These are all possible sources of CUP.

Melanoma, a type of skin cancer, could be linked to CUP.

Also, a certain family cancer history may be a risk factor. If more than one close relative, such as a grandparent, parent, or sibling, has been diagnosed with colorectal, ovarian, or breast cancer, you may have a higher risk of cancer. If you have a relative who has or had CUP, your risk for it is higher. Having a relative with CUP also increases your risk for lung, colon, and pancreatic cancers.

To lower your risk for cancer, including CUP:

• Don't smoke or use any form of tobacco or nicotine. If you do, get help to quit.
• Follow a healthy diet. Eat more fruits and vegetables.
• Get to or stay at a healthy weight for you. Ask your doctor for help.
• Get regular exercise.
• Use broad-spectrum sunscreen with SPF 30 or higher.
• Follow safety precautions to limit your exposure to chemicals at home and at work.

Talk with your doctor about your cancer risk factors. Your doctor can tell you how to help lower your risk.