What is Anal Cancer?

Introduction to Anal Cancer

Anal cancer, an uncommon cancer, is a disease in which cancer (malignant) cells are found in the anus. The anus is the opening at the end of the rectum (the end part of the large intestine) through which body waste passes. Cancer in the outer part of the anus is more likely to occur in men; cancer of the inner part of the rectum (anal canal) is more likely to occur in women. If the anus is often red, swollen, and sore, there is a greater chance of getting anal cancer. Tumors found in the area of skin with hair on it just outside the anus are skin tumors, not anal cancer.

A doctor should be seen if one or more of the following symptoms appear: bleeding from the rectum (even a small amount), pain or pressure in the area around the anus, itching or discharge from the anus, or a lump near the anus.

If there are signs of cancer, a doctor will usually examine the outside part of the anus and give a patient a rectal examination. In a rectal examination, a doctor, wearing thin gloves, puts a greased finger into the rectum and gently feels for lumps. The doctor may also check any material on the glove to see if there is blood in it. The doctor may give the patient general anesthesia, medicine that puts patients to sleep, to continue the examination if pain is felt during it. The doctor may cut out a small piece of tissue and look at it under a microscope to see if there are any cancer cells. This procedure is called a biopsy.

Anal cancer is an uncommon malignancy, accounting for only a small percentage (4%) of all cancers of the lower alimentary tract. Clinical trials have evaluated the roles of chemotherapy, radiation therapy, and surgery
in the treatment of this disease.

Overall, the risk of anal cancer is rising, with data suggesting that individuals with human papillomavirus, and male homosexuals in particular, are at increased risk of anal cancer.

The prognosis (chance of recovery) and choice of treatment depend on the stage of the cancer (whether it is just in the anus or has spread to other places in the body) and the patient’s general health.

Anal cancer is an often curable disease. The 3 major prognostic factors are site, size, and differentiation (well-differentiated tumors are more favorable than poorly differentiated tumors). Squamous cell (epidermoid) carcinomas make up the majority of all primary cancers of the anus. The important subset of cloacogenic (basaloid transitional cell) tumors constitute the remainder. These two histologic variants are associated with human papillomavirus infection. Adenocarcinomas from anal glands or fistulae formation and melanomas are rare. Treatment of anal melanoma is not included in this summary.

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