Anal Cancer Overview

The vast majority of anal cancers are caused by infection with human papillomavirus (HPV). About 40 HPV types specifically infect the anogenital and upper digestive tract and are sexually transmitted. Most of the time, a healthy immune system will clear the virus, but in some cases infection can persist and lead to anal squamous intraepithelial lesions (SIL). This is particularly common in people living with HIV or people on medications that affect the immune system. Low-grade SIL (or LSIL) include genital warts or condylomata and are considered benign, although they can greatly impact quality of life. High-grade SIL (or HSIL) are anal cancer precursor lesions with the potential to develop into invasive anal cancer over time.

How it starts

Anal cancer starts when healthy cells that form the lining of the anal canal mutate into abnormal cells and grow out of control and do not die. This usually leads to the formation of a lump or mass known as a tumor. These cancerous cells can also invade areas nearby like the sphincter muscles and layers of the anus. It can also spread to other parts of your body. This is known as metastasis. 

Anal cancer is also referred to as squamous cell carcinoma of the anus.

Anal cancer is sometimes confused with rectal cancer because of how close they are anatomically, but the two diseases and treatments are not the same.

Human papillomavirus (HPV) is detected in a majority of anal cancers and is the most common cause of anal cancers.

Symptoms of anal cancer

At the earliest stages of anal cancer, sometimes patients will have no symptoms until it grows or spreads. Common symptoms include:

  • Pain, pressure or localized tenderness around anal area that is constant, worsened with bowel movements, or during anal receptive intercourse
  • Change in bowel habits including bleeding from the anus, narrowers stools, bleeding with bowel movements
  • A lump increasing in size around your anal area
  • Pain when sitting for long periods of time, sense of fullness and constant need to evacuate stool
  • Swollen lymph nodes near your anal and/or groin area

There are several causes of these symptoms but is important to urgently follow up with your healthcare provider if you develop any of these symptoms and are at risk for anal cancer.