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Anal cancer is a disease in which malignant (cancer) cells form in the tissues of the anus.
The anus is the end of the large intestine, below the rectum, through which stool (solid waste) leaves the body. The anus is formed partly from the outer, skin layers of the body and partly from the intestine. Two ring-like muscles, called sphincter muscles, open and close the anal opening to let stool pass out of the body. The anal canal, the part of the anus between the rectum and the anal opening, is about 1½ inches long.
The skin around the outside of the anus is called the perianal area. Tumors in this area are skin tumors, not anal cancer.
Symptoms and Diagnosis
These and other symptoms may be caused by anal cancer. Other conditions may cause the same symptoms. A doctor should be consulted if any of the following problems occur:
- Bleeding from the anus or rectum.
- Pain or pressure in the area around the anus.
- Itching or discharge from the anus.
- A lump near the anus.
- A change in bowel habits.
To diagnose anal cancer, the following tests and procedures may be used:
- Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient's health habits and past illnesses and treatments will also be taken.
- Digital rectal examination (DRE): An exam of the anus and rectum. The doctor or nurse inserts a lubricated, gloved finger into the lower part of the rectum to feel for lumps or anything else that seems unusual.
- Anoscopy: An exam of the anus and lower rectum using a short, lighted tube called an
anoscope.
- Proctoscopy: An exam of the rectum using a short, lighted tube called a
proctoscope.
- Endo-anal or endorectal ultrasound: A procedure in which an ultrasound transducer (probe) is inserted into the anus or rectum and used to bounce high-energy sound waves (ultrasound) off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram.
- Biopsy: The removal of cells or tissues so they can be viewed under a microscope by a pathologist to check for signs of cancer. If an abnormal area is seen during the anoscopy, a biopsy may be done at that time.
Causes
All cancers are caused by dysfunctions of proteins involved in cell division, apoptosis, or DNA repair (see general characteristics). Dysfunctional proteins may arise from gene mutations or protein interactions with environments. The following
factors may increase the risk of developing anal cancer:
-
Being infected with human papillomavirus (HPV).
- Having many sexual partners.
- Having receptive anal intercourse (anal sex).
- Frequent anal redness, swelling, and soreness.
- Having anal fistulas (abnormal openings).
- Smoking cigarettes.
Reference:
National Cancer Institute, USA.
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