Food goes from the mouth and then, for digestion, through the stomach and small and large intestines. What’s left (waste, or feces) leaves the body through the rectum and anus, which is the opening to the outside. The anal canal, about 1.5 inches long, is the last part of the digestive tract. It helps control defecation (discharge of feces, or bowel movements). It consists of muscles, glands, nerves, and valves. Types of cancer that grow in the lining of the anus depend on the different cell types found there. Major cancers in the anal canal are epidermoid cancer, adenocarcinoma, melanoma, squamous cell carcinoma, and verrucous carcinoma.
Anal cancer is rare and occurs slightly more often in women than men.
The cause is unknown, but something happens to produce a genetic mutation in the cells of the anal canal. The mutation turns healthy cells into abnormal cancer cells. Risk factors for anal cancer include being HIV positive, anal sexual activity, many sexual partners, and anal warts from infection with human papillomavirus (HPV). Age (50 and older), smoking, history of cervical cancer, chronic inflammation of the anus, and drugs or conditions that weaken the immune (infection-fighting) system increase the risk of anal cancer.
Symptoms include bleeding, itching, or discharge from the anus. Pain in the rectum or anus or the feeling of a rectal lump or mass can also be a sign or symptom of anal cancer.
For diagnosis, the health care provider uses a medical history and physical examination including a digital rectal examination (DRE) and anoscopy. Anoscopy uses a short lighted tube to look at the area. A biopsy of the area will be done. In a biopsy, a piece of tissue is removed and a microscope is used to look for cancer cells in tissue. If cancer cells are found on the biopsy, other tests may be done including ultrasonography to see how deep the tumor is and computed tomography (CT) or magnetic resonance imaging (MRI) to find out whether the cancer has spread (staging). Checking the tumor’s stage helps the health care provider make treatment decisions.
Anal cancer is often curable. Treatment depends on tumor size, how deep the tumor is, and whether the tumor spread to lymph nodes in the groin. Older treatments mainly involved an operation to remove the tumor and tissues around it. Often, a colostomy bag was needed. Today, radiation therapy, chemotherapy, and limited surgery allow most of the anal canal to be preserved. Many people have good anal function with this combination treatment. A team of specialists involved in care includes an oncologist (who prescribes chemotherapy), radiation oncologist (who uses radiation treatment), and surgeon. Prognosis depends on the tumor’s size and spread.
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