HPV (human papillomavirus) can cause six types of cancer: cervical, vaginal, vulvar, penile, anal, and oropharyngeal (the back of the throat, including the base of the tongue and tonsils). Together, these account for tens of thousands of cancer diagnoses in the United States each year. Not every HPV infection leads to cancer, but certain high-risk strains of the virus are responsible for the vast majority of cases at these six sites.
How HPV Turns Into Cancer
Most people who get HPV never develop cancer. The immune system clears the majority of infections within about 16 months on average. The problem starts when a high-risk strain of HPV persists in the body for years instead of being cleared. During that time, the virus produces two proteins that essentially disable your cells’ built-in cancer defenses. One protein breaks down p53, a molecule that normally detects DNA damage and triggers repair or cell death. The other disables a second safeguard called pRb, which controls when cells divide. With both of these protective systems knocked out, infected cells can accumulate genetic damage and multiply unchecked.
This process is slow. It typically takes years, sometimes decades, for a persistent HPV infection to progress through precancerous changes and into invasive cancer. That long timeline is what makes screening so effective for cervical cancer: there’s a wide window to catch and treat abnormal cells before they become dangerous.
Which HPV Strains Are Most Dangerous
There are over 200 types of HPV, but only about 14 are classified as high-risk for cancer. HPV 16 is by far the most dangerous, responsible for roughly 50% of cervical cancers worldwide and the dominant strain in most other HPV-related cancers. HPV 18 is the second most common; together, types 16 and 18 account for about 66% of cervical cancers. Five additional strains (types 31, 33, 45, 52, and 58) cause another 15% of cervical cancers and 11% of all HPV-associated cancers combined. High-risk HPV types are detected in 99% of cervical precancers.
Cervical Cancer
Cervical cancer is the most strongly linked cancer to HPV. Persistent HPV infection causes about 95% of all cervical cancers, according to the World Health Organization. This makes it one of the few cancers with a near-singular cause, which is why HPV screening has become central to cervical cancer prevention. The infection typically begins in the transformation zone where the outer surface of the cervix meets the inner canal, and precancerous changes can be detected years before they would become invasive.
Oropharyngeal Cancer
Cancers of the oropharynx, the region that includes the base of the tongue, tonsils, and soft palate, are now the most common HPV-related cancer in the United States by sheer numbers. About 22,585 oropharyngeal cancers are diagnosed annually, and roughly 70% of them (around 16,000 cases) are attributable to HPV. These cancers occur more often in men than women, and HPV-positive oropharyngeal cancers tend to respond better to treatment than those caused by tobacco or alcohol use. Unlike cervical cancer, there is currently no approved screening test for HPV-related throat cancers, so most are found when symptoms like a persistent sore throat, difficulty swallowing, or a lump in the neck prompt a visit to a doctor.
Anal Cancer
HPV causes the vast majority of anal cancers. The virus infects the lining of the anal canal in much the same way it affects the cervix, and like cervical cancer, anal cancer develops through a precancerous stage that can potentially be detected through screening. People who are at higher risk include those with HIV, men who have sex with men, and anyone with a weakened immune system. Some medical centers now offer anal Pap tests to screen high-risk populations, though this practice is not yet as standardized as cervical cancer screening.
Vaginal and Vulvar Cancers
HPV causes a significant share of vaginal and vulvar cancers, though these are less common than cervical or oropharyngeal cancers. Vulvar cancer may appear as a persistent lump, sore, or area of thickened skin on the vulva, while vaginal cancer can cause unusual bleeding or discharge. Both tend to develop slowly from precancerous changes, similar to the progression seen in cervical cancer. Not all vulvar and vaginal cancers are HPV-related; some arise through other pathways, particularly in older women.
Penile Cancer
Penile cancer is rare in the United States and other developed countries, but HPV is a major cause when it does occur. It most often affects the foreskin or the head of the penis. Risk factors beyond HPV include being uncircumcised, smoking, and poor hygiene. Because of its rarity, there is no routine screening program, and early signs like changes in skin color, thickening, or a sore that doesn’t heal are the typical reasons someone seeks evaluation.
HPV Vaccination and Cancer Prevention
The HPV vaccine targets the high-risk strains most responsible for cancer, including types 16 and 18. Vaccination has already produced measurable results. In the United States, cervical precancer rates among screened women aged 18 to 20 dropped by 50% between 2008 and 2015, and by 36% among women aged 21 to 24 over the same period. The percentage of cervical lesions caused by vaccine-targeted HPV types has fallen by 40% in vaccinated women since the vaccine was introduced. Data from Sweden and Denmark show that women vaccinated in their teens have a lower risk of cervical cancer as adults.
The vaccine is most effective when given before exposure to HPV, which is why it’s recommended for preteens around age 11 or 12, though it can be given up to age 26 for most people and up to 45 in some cases. Because the vaccine prevents the initial infection, it protects against all six HPV-related cancer types, not just cervical cancer. For cancers without screening tests, like oropharyngeal and penile cancer, vaccination is currently the only preventive tool available.