Merck Manual

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Anal Cancer

By

Anthony Villano

, MD, Fox Chase Cancer Center

Reviewed/Revised Oct 2023
VIEW PROFESSIONAL VERSION
  • Risk factors for anal cancer include certain sexually transmitted infections.

  • 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 Rectum and Anus The rectum is a chamber that begins at the end of the large intestine, immediately following the sigmoid colon, and ends at the anus ( Home.see also page Overview of the Anus and Rectum). Ordinarily... read more and the rectum Rectum and Anus The rectum is a chamber that begins at the end of the large intestine, immediately following the sigmoid colon, and ends at the anus ( Home.see also page Overview of the Anus and Rectum). Ordinarily... read more (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 9,760 people in the United States each year and causes about 1,870 deaths. Anal cancer is more common among women.

Risk factors for anal cancer include the following:

Symptoms of Anal Cancer

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.

Diagnosis of Anal Cancer

  • A doctor's evaluation

  • Sigmoidoscopy or colonoscopy

  • Biopsy

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).

Once anal cancer is diagnosed, other imaging tests, such as computed tomography (CT) or magnetic resonance imaging (MRI), are done to determine whether the cancer has spread (metastasized).

Treatment of Anal Cancer

  • Combination of chemotherapy and radiation therapy (called chemoradiation)

  • Sometimes surgery

The treatment of and prognosis for anal cancer depend on the extent of the cancer.

Chemoradiation is usually done first. Tumors continue to shrink for up to 6 months after chemoradiation is completed.

Surgery is done in people whose cancer does not go away after chemoradiation 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). A sphincter that does not function properly could lead to loss of control over bowel movements (fecal incontinence Fecal Incontinence Fecal incontinence is the loss of control over bowel movements. Fecal incontinence can occur briefly during bouts of diarrhea or when hard stool becomes lodged in the rectum ( fecal impaction)... read more ).

NOTE: This is the Consumer Version. DOCTORS: VIEW PROFESSIONAL VERSION
VIEW PROFESSIONAL VERSION
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