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A risk factor is anything that affects your chance of getting a disease like cancer. Different cancers have different risk factors. Some cancer risk factors, like smoking or sun exposure, can be changed. Others, like a person’s age or family history, can’t be changed.

But having a risk factor, or even many, doesn't mean that you will get the disease. On the other hand, some men who develop penile cancer have no known risk factors.

Scientists have found certain risk factors that make a man more likely to develop penile cancer.

Human papillomavirus (HPV) infection

Human papillomavirus (HPV) is a group of more than 150 related viruses. They are called papillomaviruses because some of them cause growths called papillomas (more commonly called warts). Different HPV types cause different types of warts in various parts of the body. Certain HPV types can infect the genital organs and the anal area, causing raised, bumpy warts called condyloma acuminata (or just condylomas).

Other HPV types have been linked with certain cancers. For example, infection with some types of HPV appears to be an important risk factor for penile cancer. In fact, HPV is found in about half of all penile cancers.

HPV is passed from one person to another during skin-to-skin contact with an infected area of the body. HPV can be spread during sexual activity – including vaginal, anal, and oral – but sex doesn’t have to occur for the infection to spread. All that's needed is skin-to-skin contact with an area of the body infected with HPV. Infection with HPV can also spread from one part of the body to another. For example, infection may start in the penis and then spread to the anus.

HPV infection is common. In most men, the body clears the infection on its own. But in some, the infection doesn't go away and becomes chronic. Over time, chronic infection, especially with certain HPV types, can cause some types of cancer, including penile cancer. Men who are not circumcised may be more likely to get and stay infected with HPV.

To learn a lot more, see our HPV section.

Not being circumcised

Circumcision removes all (or part) of the foreskin. This procedure is most often done in infants, but it can be done later in life, too. Men who were circumcised as children may have a much lower chance of getting penile cancer than those who were not. In fact, some experts say that circumcision as an infant prevents this cancer. The same protective effect is not seen if circumcision is done as an adult.

The reason for the lower risk in circumcised men is not entirely clear, but it may be related to other known risk factors. For example, men who are circumcised can’t develop the condition called phimosis, and they don’t accumulate material known as smegma (see the next section). Men with smegma or phimosis have an increased risk of penile cancer. The later a man is circumcised, it's more likely that one of these conditions will occur first.

In weighing the risks and benefits of circumcision, doctors consider the fact that penile cancer is very uncommon in the United States, even in uncircumcised men. Although the American Academy of Pediatrics has stated that the health benefits of circumcision in newborn males outweigh the risks, it also states these benefits are not great enough to recommend that all newborns be routinely circumcised. In the end, decisions about circumcision are highly personal and often depend more on social and religious factors than on medical evidence.

Phimosis and smegma

Uncircumcised men with certain conditions are at higher risk for penile cancer.

Phimosis

In men who are not circumcised, the foreskin can sometimes become tight and difficult to retract. This is known as phimosis. Penile cancer is more common in men with phimosis. The reason for this is not clear, but it might be related to the build-up of smegma or from inflammation that results from phimosis.

Smegma

Sometimes secretions can build up underneath an intact foreskin. If the area under the foreskin isn’t cleaned well, these secretions build up enough to become a thick, sometimes smelly substance called smegma. Smegma is more common in men with phimosis, but can occur in anyone with a foreskin if the foreskin isn't retracted regularly to clean the head of the penis.

In the past some experts were concerned that smegma might contain compounds that can cause cancer. Most experts now believe that smegma itself probably doesn’t cause penile cancer. But it can irritate and inflame the penis, which can increase the risk of cancer. It might also make it harder to see very early cancers.

Smoking and other tobacco use

Men who smoke and/or use other forms of tobacco are more likely to develop penile cancer. Tobacco users who have HPV infections have an even higher risk. Tobacco use exposes your body to many cancer-causing chemicals. These harmful substances are inhaled into the lungs, where they are absorbed into the blood, or they're absorbed through mouth tissues into the blood. They can travel in the bloodstream throughout the body to cause cancer in many different areas. Researchers believe that these substances damage genes in cells of the penis, which can lead to penile cancer.

UV light treatment of psoriasis

Men who have a skin disease called psoriasis are sometimes treated with drugs called psoralens and then an ultraviolet A (UVA) light source. This is called PUVA therapy. Men who have had this treatment have been found to have a higher rate of penile cancer. To help lower this risk, men being treated with PUVA now have their genitals covered during treatment.

Age

The risk of penile cancer goes up with age. In the US, the average age of a man when he is diagnosed is about 68. About 4 out of 5 penile cancers are diagnosed in men over age 55.

AIDS

Men with AIDS have a higher risk of penile cancer. This higher risk seems to be linked to their weakened immune system, which is a result of this disease. But it might also be linked to other risk factors that men with HIV (the virus that causes AIDS) are more likely to have. For example, men with HIV are more likely to smoke and be infected with HPV.