Gastrointestinal tract anatomy, colon, appendix, rectum and anus
Figure 1. Intestinal tract, including colon, appendix, rectum and anus

What is anal dysplasia?

Dysplasia refers to any kind of abnormal changes in the cells of the body. Anal dysplasia, anal intraepithelial neoplasia (AIN) and anal squamous intraepithelial lesion (SIL) are terms used to describe conditions that occur before the onset of anal squamous cell cancer (SCC). As shown in Figure 1, the anus is located at the end of the intestinal tract. The anus is the part of the rectum that allows stool to pass outside of the body.

The human papilloma virus (HPV) infects the lowest cell layer of the skin, the basement membrane. As shown in Figure 2, precancerous cells expand to the surface. Figure 2 also gives other names to describe this process and shows the grades of dysplasia. For instance, condyloma (warts) are considered to be a form of mild dysplasia. These warts are not cancer, but they do indicate an HPV infection.

Anal Cancer Pathogenesis

Figure 2. LSIL stands for low-grade squamous intraepithelial lesion. HSIL stands for high-grade squamous intraepithelial lesion. The figure shows the point that HPV infects the lowest level of skin cells (basement membrane). The figure also shows that the infected cells move up to the skin surface. The infected cells also grow beneath the basement membrane, which is the point at which cancer begins.

In addition to anal cancer, HPV infection is associated with other types of cancers, including cancers of the urinary system, sex organs, and head and neck. HPV infection is common. Most sexually active US adults will get HPV at some time in their lives.

What are the risk factors for developing anal dysplasia and/or anal cancer?

There are several risk factors (things that make your chance of getting a disease more likely) related to anal dysplasia and anal cancer. These include:

  • Becoming infected with human papillomavirus (HPV)
  • Having a higher number of sexual partners
  • Having anoreceptive intercourse (being the receiving partner in anal sex)
  • Using tobacco
  • Having anal wounds that have not healed
  • Having dysplasia of the genitals
  • Being immunosuppressed due to:

How common is anal cancer?

According to the American Cancer Society, there will be about 8,300 new cases diagnosed in 2019 in the United States, with about 1,280 people dying from the disease. The incidence of anal cancer has been rising.

What are the symptoms of anal dysplasia?

Anal dysplasia often causes no symptoms. When symptoms are present, they may include:

  • Anal itching (also called pruritus)
  • Pressure—a feeling that there is a lump or mass in the anus
  • Pain

What are the symptoms of anal cancer?

  • A lump in or near the anus
  • Bleeding from the rectum or the anus
  • Discharge from the anus

It is important to note that most of these symptoms and signs can be caused by less severe conditions. That is why you should contact your doctor to be examined so that the correct diagnosis can be made.

Last reviewed by a Cleveland Clinic medical professional on 03/27/2019.


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