Anal Cancer

Although rare, anal cancer is becoming more prevalent in the United States and many other developing countries. The condition develops in the tissues of the anus, which is a short tube that connects the lower part of the large intestine, known as the rectum, to the outside of the body. The anus allows the controlled disposal of body waste during bowel movements.

Like cervical cancer, the principal cause of anal cancer is human papillomavirus (HPV), a common virus that causes changes in the skin. Anal HPV infection is most commonly acquired through anal intercourse, but it can also be acquired from other genital areas that are infected, particularly from the vulva in women, or from the penis in men. Fingers and toys can probably lead to anal HPV infection as well.

Research suggests that sexually active individuals, both men and women, may be at risk for HPV. The good news is that only a fraction of people with anal HPV infection will develop a lasting case of anal intraepithelial neoplasia (AIN) — a precursor to anal cancer — and even fewer will develop anal cancer.

Other risk factors for anal cancer include:

• Men and women with a history of anal intercourse
• Men and women with a history of perianal warts, which are found outside the anus
• Women with a history of vulvar warts, which are found outside the female genitals
• Men and women who are chronically immunocompromised, such as those taking immunosuppressive medications, and those who are HIV positive, or those have received organ transplants

Additional risk factors include being over 50 years of age, having many sexual partners and smoking, which increases a person's chance of developing HPV.

Our Approach to Anal Cancer

At UCSF, we specialize in the early detection and treatment of anal cancer, a rare cancer that's becoming more common. In addition, we help patients avoid anal cancer by finding and managing precancerous conditions. We are also active in research to develop more effective therapies for those conditions.

Our team includes experts with decades of experience specifically focused on anal cancer and HPV (human papillomavirus), which causes most anal cancers. We pioneered the use of a tool called a colposcope for diagnosing HPV-related diseases, as well as high-resolution anoscopy, considered the best technique for anal cancer screening.