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The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on April 2, 2021.

About anal cancer

This rare form of cancer develops in the tissues of the anus, the opening at the end of the rectum through which stool passes. About one in 500 men and women will develop anal cancer in his or her lifetime, according to the American Cancer Society

Experts estimate there will be 9,090 new cases of anal cancer diagnosed in the United States in 2021. Women will make up the majority of cases (6,070). The catalyst for 95 percent of anal cancers is infection with the human papillomavirus (HPV) from a sexual partner, according to the National Cancer Institute.

What causes anal cancer?

Known risk factors for anal cancer include chronic infection with HPV, gender and age. HPV infection spreads primarily through vaginal, oral or anal sex. The HPV vaccine provides protection against many strains of the virus.

Other common risk factors for anal cancer include:

  • A compromised immune system, often caused by HIV (human immunodeficiency virus) infection, immunosuppressants or an organ transplant
  • Anal intercourse
  • Other gynecologic cancers, such as cervical cancer, vulvar cancer or vaginal cancer
  • Chronic local inflammation, such as anal fistulas or long-lasting open wounds

Who gets anal cancer?

Two-thirds of anal cancer cases occur in people older than 55. The average age for diagnosis is in the early-60s, according to the National Cancer Society. Women are at greater risk than men.

Smokers have a higher risk of anal cancer, but that risk decreases significantly when smokers quit. Anal cancer is more prevalent among African Americans than in whites.

Anal cancer types

The forms of abnormal cell growth in the anus are anal intraepithelial neoplasia (AIN) or anal squamous intraepithelial lesions (SILs). Tumors in or on the anus may be benign tumors (noncancerous) or malignant tumors (cancerous).

The different types of anal cancer, and where they show up, include:

  • Squamous cell carcinoma, found in the outer lining of the anal canal
  • Cloacogenic carcinoma, found between the outer part of the anus and the lower part of the rectum
  • Adenocarcinoma, found in mucus-producing glands beneath the anal lining
  • Basal cell carcinoma, a skin cancer, found in the perianal skin around the anus.
  • Melanoma, a skin cancer, found in pigment-producing cells in the skin or anal lining

Squamous cell carcinoma is the most common type of anal cancer. Carcinoma in situ, also called high-grade squamous intraepithelial lesions or Bowen disease, refers to precancerous cells found on the inner surface of the anus.

Anal cancer symptoms

Early detection of anal cancer is common. The first indication of anal cancer is often rectal bleeding, which occurs in more than half the patients. Symptoms of anal tumors are often similar to benign conditions, such as hemorrhoids, anal fissures, fistulas and anal warts, so it’s important to discuss your symptoms with your doctor.

Besides rectal bleeding, symptoms of anal cancer may include:

  • Persistent or recurring anal itching
  • Persistent or recurring pain in the anal area
  • Feeling of a lump or mass in the anus
  • Change in bowel habits (going to the bathroom more or less frequently) or increased strain during bowel movement
  • A narrowing of the diameter of stool
  • Abnormal discharge from the anus
  • Swollen lymph nodes in the anal or groin area

Diagnosing anal cancer

Our pathologists at CTCA® perform a comprehensive physical exam and conduct a series of tests to diagnose anal cancer.

Those tests for diagnosing anal cancer may include:

  • Biopsy of anal tissue
  • Digital rectal exam (DRE)
  • Magnetic resonance imaging (MRI)
  • Computed tomography scan (CT scan)
  • Positron emission tomography scan (PET scan)
  • Anoscopy

Treating anal cancer

According to the American Cancer Society, the 5-year survival rate for anal cancer ranges from 32%, for cancer that has spread to distant parts of the body, to 82%, for cancer that has not spread outside beyond the anal area.

In the past, surgery was the only treatment for anal cancer patients. Treatment options today often involve a combination of radiation therapy and chemotherapy.

Two types of surgical procedures may be used in anal cancer treatment:

  • A local resection treats cancers in the lower part of the anal canal, known as the anal margin, and may be an option for early-stage cancer.
  • An abdominoperineal resection, involving the removal of the anus and anal sphincter, may be an option for recurrent cancer or cancer that has not responded to other treatments.

The oncologists on your CTCA care team may recommend chemoradiation, a combination of radiation and chemotherapy, instead of surgery. Surgery may involve a permanent colostomy, which requires a bag attached to the abdomen to collect stool. The bag sits outside the body and connects to the end of the large intestine, through a permanent opening in the abdomen called a stoma.

Chemotherapy drugs target cancer cells to destroy them or lessen their ability to grow and reproduce. Radiation therapy allows oncologists to target difficult-to-reach tumors with X-rays and other forms of radiation while reducing exposure to healthy tissue.