- Risk factors for anal cancer include certain sexually transmitted diseases.
- Bleeding with bowel movements, pain, and sometimes itching around the anus are typical symptoms.
- A manual examination, sigmoidoscopy or colonoscopy, and a biopsy are done to verify the diagnosis.
- Treatment may involve either surgery alone or a combination of radiation therapy and chemotherapy or radiation therapy and surgery.
Anal cancer develops in the skin cells of the immediate area around the anus or in the lining of the transitional zone between the anus and the rectum (the anal canal). Unlike in the rectum and the large intestine, in which cancers are almost always adenocarcinomas, cancers of the anus are primarily squamous cell carcinomas.
Anal cancer occurs in about 8,580 people in the United States each year and causes more than 1,160 deaths. Anal cancer is more common among women.
Risk factors for anal cancer include the following:
- Human papillomavirus (HPV) infection (genital warts)
- Receptive anal intercourse
- Chronic fistulas
- Received radiation therapy on anal skin
- Lymphogranuloma venereum infection
- Human immunodeficiency virus (HIV) infection
People with anal cancer often experience bleeding with bowel movements, pain, and sometimes itching around the anus. About 25% of people with anal cancer have no symptoms. In this instance, the cancer is found only during a routine examination.
- A doctor's evaluation
- Sigmoidoscopy or colonoscopy
To diagnose anal cancer, a doctor first inspects the skin around the anus for any abnormalities. With a gloved hand, the doctor probes the anus and lower rectum, checking for any portions of the lining that feel different from surrounding areas. A flexible sigmoidoscope (a short viewing tube with a camera on the end) is used to evaluate the anus and rectum. An anoscope (a small rigid tube equipped with a light) may be inserted several inches into the anus to assist with examination.
The doctor then removes a sample of tissue from an abnormal area and examines it under a microscope (called a biopsy).
If people have bleeding, doctors may do a colonoscopy to look for a coexisting colon cancer. During a colonoscopy, the entire large intestine is examined. A colonoscopy may be done even in people with who have obvious hemorrhoids (twisted veins located in the wall of the rectum and anus), which can cause bleeding.
- Combination of radiation with chemotherapy
- Sometimes surgery
The treatment and prognosis of anal cancer depends on the extent of the cancer.
Radiation therapy combined with chemotherapy is usually done first.
Surgery is done in people whose cancer does not go away after radiation therapy and chemotherapy or goes away and comes back. With surgery, the doctor must be careful not to interfere with the functioning of the muscular ring that keeps the anus closed (the anal sphincter). The anal sphincter stays closed until the person has a bowel movement. A sphincter that does not function properly could lead to loss of control over bowel movements (fecal incontinence).
For people whose cancer has not spread, therapy cures many anal cancers, with 70% or more of people surviving longer than 5 years.
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