After a bowel movement, if a person notices blood in the toilet—or on toilet paper—they may assume they have hemorrhoids. While, in many cases this is true, it is always something you should have checked out by a doctor as some people who experience rectal bleeding may have anal cancer.

Anal cancer is slightly more common among women than men, and age is a factor—it’s more common among people in their 50s and 60s than in younger adults.

Anal cancer is a rare type of cancer that affects about 9,000 Americans annually, but it is on the rise. The past two decades have seen the number of cases climb.

The good news is that anal cancer responds well to early treatment. Between 74 and 90% of people with anal cancer may be cured when they’re diagnosed and treated early.

Anal cancer is the name for different cancers that affect the mucous membranes within the anus, including the short internal tube at the end of the digestive tract known as the anal canal, along with the anal opening (and a portion of exterior skin just outside of it).

The anus is the final portion of the digestive tract. Internally, the anal canal is connected to the rectum, which is, in turn, connects to the sigmoid colon, a part of the large intestine. Feces leave the body through the anal opening. Changes to cells within any portion of the anus may lead to cancer.

Roughly 80% of anal cancer is classified as squamous cell carcinoma, a common skin cancer. Some people may have adenocarcinoma, a type of cancer that begins in mucus-producing glands. Even fewer people may have anal melanoma, an aggressive form of skin cancer.

Most cases of anal cancer are linked to the presence of human papillomavirus (HPV), which is the most common sexually transmitted infection. The majority of sexually active people are exposed to HPV at some point in their lives. Most people who are infected don’t experience symptoms, and their bodies clear the virus without any real indication that they had it. There are dozens of HPV subtypes, many of which don’t cause health problems or complications.

However, some types of HPV are more serious than others, and the virus is linked to a variety of potential medical problems. Some HPV subtypes may cause genital warts. Other HPV subtypes may cause cancer, including cervical, vulvar, vaginal, penile, or anal cancer. People may not develop cancer for years after becoming exposed to HPV. Over time, the presence of HPV in the body may lead to inflammation, which may cause abnormal cells to develop that eventually change to cancer. Two HPV subtypes—HPV-16 and HPV-18—have been linked to most cases of anal cancer.

Only certain people who have been exposed to HPV-16 or HPV-18 may develop anal or other types of cancer. People with weakened immune systems are at greater risk. Having more sexual partners increases the risk, because it may increase a person’s exposure to different subtypes of HPV.

Most people with anal cancer experience rectal bleeding but there are some individuals who have no noticeable early symptoms.

Other common symptoms include:

• Anal pain or discomfort
• Abdominal cramping
• The urge to make a bowel movement, even after finishing
• A change to bowel habits
• Anal discharge
• A palpable anal mass, which may or may not bleed
• Enlarged local lymph nodes

People are at greater risk of anal cancer if they have had:

• Multiple sexual partners
• Receptive anal sex (including men having sex with men)
• A history of sexually transmitted infections
• A history of cancer of the cervix, vagina, or vulva
• An HIV diagnosis
• A suppressed immune system
• An organ transplant (especially if it happened 10 or more years earlier)
• Anal fissures, fistulas, or hemorrhoids

Smoking cigarettes may also increase the risk of anal cancer.

When doctors suspect anal cancer, they want to find out as much about a patient’s medical history as possible. They may ask about a history of HIV, different types of cancer, sexually transmitted infections, or digestive disease. They may also ask about a person’s sexual history, including the number of sexual partners they have had and whether male patients have had sex with other men.

During a physical exam, a doctor may perform:

• A digital rectal exam, to feel for any abnormalities, swollen lymph nodes or tumors
• Anoscopy or proctoscopy, to view the interior of the anus

A doctor may order the following imaging test to confirm the presence of anal cancer:

• A CT scan of the chest, abdomen, and pelvis
• An MRI or PET scan of the pelvis
• An X-ray of the chest and abdomen, if the doctor suspects that the cancer has spread to the lungs

When evidence of a tumor is found during an imaging test, doctors biopsy the tissue to confirm the presence of anal cancer.

Anal cancer can’t be diagnosed with a blood test, but doctors sometimes order blood tests to check for HIV, which may increase the risk of anal cancer.

Some doctors also recommend a Pap test for female patients. The test checks for cervical cancer, which is also caused by HPV.

In most cases, people with anal cancer will spend a 4- to 8-week time period undergoing both chemotherapy and radiation treatments known as external beam radiation therapy.

Some individuals undergoing treatment may receive a temporary, reversible colostomy. For a short time, fecal waste is collected in a bag, which people must empty themselves, and then the procedure is reversed.

If chemotherapy plus radiation isn’t effective after a set period of time, or if anal cancer recurs, a person may need to have the anus, rectum and a portion of the sigmoid colon surgically removed (surgical resection). This procedure results in permanent colostomy.

However, when anal cancer is identified early, and the tumor or lesion is small and located on the skin near the anal opening (rather than within the anal canal), it may be surgically removed. This is only considered if surgery can be done without damaging the muscles of the anal sphincter, which control the ability to allow for bowel movements. When surgery is done, the patient typically doesn’t need chemotherapy or radiation afterwards.

Most people with anal cancer recover completely, although there is a chance that the cancer may recur. Many people won’t experience any long-lasting effects from anal cancer. However, if surgery is required to remove diseased portions of the digestive tract, they may receive a permanent colostomy.

“The treatment of anal cancer is multimodal, requiring close collaboration between medical oncologists, radiation oncologists, and surgeons,” says George Yavorek, MD, the medical director of Colorectal Surgery. “There are several treatment regimens involving surgery, chemotherapy, radiation, and possibly immunotherapy that are tailored to the individual patient for treatment of both locoregional and advanced disease. Having a number of specialists in each of these disciplines who meet and work together constantly, the anal cancer program at the Smilow Cancer Hospital at Yale has extensive experience and success in this area. I believe this makes Yale the go-to place for patients with this diagnosis.”