Cancer of the Anus
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 the rectum and the large intestine, in which cancers are almost always adenocarcinomas, cancers of the anus are primarily squamous cell carcinomas.
Cancer of the anus occurs in about 1 of 100,000 people in the United States each year. Anal cancer is almost twice as common in women as in men. The cause of anal cancer is unknown. Receptive anal intercourse has been linked to anal cancer, and infection with a specific type of sexually transmitted human papillomavirus (HPV type 16) has been identified as a likely cause.
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 these instances, 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).
Treatment
Radiation therapy combined with chemotherapy may be used instead of or in addition to surgery. Surgery alone is avoided so as 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 recurrence of the cancer.
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