Anal Cancer

Medically reviewed by: Gary H. Hoffman, MD

Anal cancer is a rare disease, with about 3,400 new cases every year. This accounts for up to two percent of all gastrointestinal cancers annually. When diagnosed early with a routine screening like colonoscopy or digital rectal exam and anoscopy, anal cancer can be highly treatable.

What is Anal Cancer?

Anal cancer is a rare form of cancer that develops in the anal canal or passageway, the short tube connecting the rectum to the buttocks.

The two most common types of anal cancer are squamous cell carcinoma, which develops in the skin cells, and cloacogenic carcinoma, a condition marked by growths in the tissue lining the anal canal. If anal cancer is diagnosed before malignant cells have invaded the surface of the anal lining, it is known as Bowen’s disease, a pre-cancerous condition.

Common symptoms of anal cancer include:

  • Anal bleeding
  • Pain surrounding the anus
  • Anal itching
  • Mucous in stool
  • Straining during bowel movements
  • Changes in bowel habits, including narrowing of stool

In many cases of anal cancer, a small growth becomes noticeable along the anal canal. To diagnose anal cancer, your physician may use a small lighted tube called an anoscope to examine the anal canal and rectum and take a biopsy of any abnormalities.

Who is at Risk for Anal Cancer?

Anal cancer is a genetic mutation that develops in the cells of the anal canal and is closely related to the sexually-transmitted human papilloma virus or HPV. While the exact cause of anal cancer is unknown, HPV is detected in most cases of anal cancer and is thought to be the leading risk factor for the disease.

Other risk factors for anal cancer include:

  • Use of immunosuppressive drugs
  • Anal or genital warts
  • Anal sex and history of many sexual partners
  • Being over the age of 50
  • HIV

In addition to the above factors, those with chronic anal inflammation due to anal fistulas or open wounds are at an increased risk of developing anal cancer. Those with a history of rectal, prostate, bladder or cervical cancer who have received radiation treatment for those conditions are also at an increased risk of developing anal cancer.

Diagnosis and Treatment of Anal Cancer

Routine screening for anal cancer may include a digital rectum exam, stool test or flexible endoscopy examination. Individuals with a history of anal warts or HPV should have annual or digital rectal exams and anal pap smears.

Treatment for anal cancer especially when found early involves use of radiation and chemotherapy. Early lesions respond extremely well and no surgery is required. Most patients who undergo treatment for anal cancers are able to retain control over their bowel movements. Surgery which typically would include resection of the anus and rectum with permanent colostomy formation is reserved for individuals who do not respond to chemoradiation therapy.

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