A risk factor is anything that increases your 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, bladder, kidney, and several other organs. But having a risk factor, or even several, does not mean that you will get the disease.

Scientists have found certain risk factors that make a man more likely to develop penile cancer. Even if a person does have one or more risk factors for penile cancer, it is impossible to know for sure how much that risk factor contributes to causing the cancer. On the other hand, some men who develop penile cancer have no known risk factors.

Local Hygiene, Phimosis, and Smegma

In men who are not circumsised and therefore, have an intact foreskin, secretions can build up underneath. This can worsen with improper cleaning. Sometimes the foreskin becomes constricted and difficult to retract. This condition is known as phimosis. Oily secretions from the skin, dead skin cells, and bacteria accumulate under the foreskin. The result is a thick, sometimes odorous substance called smegma. Some studies suggest that smegma may contain cancer-causing substances, but most recent studies disagree. Still, many doctors feel that when a man doesnÂ’t keep this area clean, he is more likely to develop cancer of the penis.

Smegma alone is unlikely to have a significant impact, if any, on your risk of developing penile cancer. Nonetheless, if uncircumcised men do not retract the foreskin and thoroughly wash the entire penis, the presence of smegma may cause irritation and inflammation of the penis. Men with phimosis are less likely to clean the penis routinely and effectively.

Human Papillomavirus Infection

Some researchers believe that infection with the human papillomavirus (HPV) may be a risk factor for penile cancer. HPVs are a group of more than 100 types of viruses called papillomaviruses because they can cause warts, or papillomas. Different HPV types cause different types of warts in various parts of the body. Some types cause common warts on the hands and feet. Other types tend to cause warts on the lips or tongue.

HPV is the major cause of cancer of the cervix in women and thought to be responsible for cancer of the anus in men and women. It may also be responsible for some cancers of the vagina and vulva in women. HPV is passed from one person to another during sexual contact. These factors can increase a person's risk of  HPV infection.

• sexual intercourse at an early age
• having many sexual partners
• having sex with a partner who has had many other partners
• having unprotected sex (not using a condom)

When HPV infects the skin of the external (outer) genital organs and anal area (around the opening of the intestinal tract), it often causes raised, bumpy warts. These may be barely visible or may be several inches across. The medical term for genital warts is condyloma acuminatum. Two "low-risk" HPV types, HPV 6 and HPV 11, cause most genital warts. These warts rarely develop into cancer. However, other sexually transmitted HPVs have been linked with genital or anal cancers in both men and women. These are called "high-risk" HPV types and include HPV 16, HPV 18, HPV 33, HPV 35, HPV 45, as well as some others.

Smoking

Smoking increases the chance of developing penile cancer. If you smoke, your body is exposed to many cancer-causing chemicals that affect more than your lungs. These harmful substances are absorbed into blood flowing through the lungs and carried in the bloodstream throughout the body. Researchers believe that these substances damage the DNA of cells in the penis and contribute to the development of penile cancer, especially in men who also have HPV infections.

UV Light Treatment of Psoriasis

Men who have a skin disease called psoriasis and who have been treated with a combination involving a drug called psoralen and exposure to ultraviolet light have a higher rate of penile cancer.

Age

Age is a risk factor. Nearly two-thirds of cases of the disease are diagnosed in men over age 65.

AIDS

Men with AIDS (acquired immunodeficiency syndrome) may have a higher risk of penile cancer. Although this may be caused by their lowered immune response, lifestyle factors may also play a role.

Not Being Circumcised

Circumcision is the removal of a part or all of the foreskin at birth or later on in life. In the United States, men who are circumcised in childhood have a lower rate of penile cancer. It’s not known whether this is due to the absence of the foreskin or other lifestyle factors. Recent studies have found that circumcised men are less likely to be infected with HPV, even after this risk is adjusted for differences in sexual behavior. Other studies suggest that circumcision may reduce the risk of more invasive forms of penile cancer. A recent study reported that uncircumcised men who had phimosis in the past were at increased risk of developing penile cancer. Penile cancer risk was not increased among uncircumcised men without phimosis.

However, it is important that the issue of circumcision not distract men from avoiding known penile cancer risk factors -- poor hygiene, phimosis, having unprotected sex with multiple partners (increasing the likelihood of human papillomavirus infection), and cigarette smoking.

In weighing the risks and benefits of circumcision, doctors consider the fact that penile cancer is one of the least common forms of cancer in the United States. Neither the American Academy of Pediatrics nor the Canadian Academy of Pediatrics recommends routine circumcision of newborns. Ultimately, decisions about circumcision are highly personal and depend more on social and religious factors than on medical evidence.