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 7,000 people in the United States each year. Anal cancer is almost twice as common among women. The cause of anal cancer is unclear, but people who practice receptive anal intercourse are at increased risk, as are those who have chronic fistulas, received radiation therapy on anal skin, leukoplakia, and certain types of sexually transmitted infections, particularly human papillomavirus (HPV type 16) and lymphogranuloma venereum (see see Lymphogranuloma Venereum).
Symptoms and Diagnosis
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.
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. The doctor then removes a sample of tissue from an abnormal area and examines it under a microscope (performs a biopsy).
Radiation therapy combined with chemotherapy may be used instead of or in addition to surgery. Surgery alone is often satisfactory treatment, although the doctor must be careful not to interfere with the functioning of the muscular ring that keeps the anus closed until the person has a bowel movement (the anal sphincter), which could lead to loss of control over bowel movements (fecal incontinence). A combination of radiation with chemotherapy, or radiation with surgery, cures many anal cancers, with 70% or more of people surviving longer than 5 years. More extensive surgery is sometimes needed if the results of follow-up biopsies performed after initial treatment show the cancer has returned.
Last full review/revision February 2013 by Elliot M. Livstone, MD