What is anal canal cancer?

The anal canal is the lowermost portion of the gastrointestinal tract, a short tube connecting the rectum to the external skin, through which stool leaves the body. It is usually around 3 to 4 cm in length and is an area of transition from the mucosa of the rectum to the anus and skin of the perianal area. It has an important function in defaecation and maintaining faecal continence. It is richly supplied by blood vessels and nerves and is usually in the collapsed position due to the contraction of the internal and external anal sphincters (muscles). Any malignancy arising in the anal canal is called an anal canal cancer.

How does anal canal cancer start?

Anal canal cancer starts when mutations in the cells of the anal canal lining turn normal cells into those with a capacity for uncontrolled multiplication. Initially, there is a pre-cancerous stage in which the tumour has not yet invaded the basement membrane of the lining epithelium. This is called Anal intraepithelial neoplasia (AIN). If not treated at this stage, they progress to become frank cancers, i.e. anal canal carcinomas. Most (80%) of anal canal cancers are squamous cell carcinomas, i.e. they are derived from the skin cells. Other rare anal canal neoplasms include adenocarcinoma, neuroendocrine tumours, malignant melanoma, lymphomas, and various mesenchymal tumours. If left neglected, as is seen in many Indian patients, the tumour then slowly increases in size and can involve the lower part of the rectum or protrude through the anus and involve the skin around the anus. It can also extend through the wall of the anal canal (destroying the internal and external anal sphincters in the process) and involve adjacent structures such as the vagina or prostate, bladder as well as lymph nodes in the groin or pelvis. It may also spread through the bloodstream to the liver, lungs, or other organs.

Can anal canal cancer be cured?

If detected in early stages, anal canal cancer can be cured with appropriate treatment, mostly combined treatment with radiation and chemotherapy.

What is the most common type of anal canal cancer?

Most (80%) of anal canal cancers are squamous cell carcinomas. Anal canal cancers are commonly caused by infection by the Human Papilloma Virus (HPV)- almost >85% of patients have HPV-positive tumours.

Symptoms (early-stage and end-stage)


Symptoms of anal canal cancer commonly include:

  • Bleeding from the anus
  • A mass protruding from the anus
  • Pain in the area of the anus
  • Anal itching
  • Lumps in the groin (due to spread to lymph nodes in the region)
  • Inability to control the passage of stools (Faecal incontinence)

Some of these symptoms may be confused with symptoms of hemorrhoids/piles and maybe neglected for long before the patient seeks appropriate medical management.

Risk Factors

Several factors have been found to increase the risk of anal cancer, including:

  • Older age. Most cases of anal cancer occur in people age 50 and older.
  • Many sexual partners. People who have many sexual partners over their lifetimes have a greater risk of anal cancer
  • Anal sex. People who engage in anal sex have an increased risk of anal cancer.
  • Smoking. Smoking cigarettes may increase the risk of anal cancer.
  • History of cancer. Those who have had cancer of the cervix, vulva or vagina have an increased risk of anal cancer.
  • Human papillomavirus (HPV). HPV infection increases your risk of several cancers, including anal cancer and cervical cancer. HPV infection is a sexually transmitted infection that can also cause genital warts.
  • Drugs or conditions that suppress your immune system. People who take drugs to suppress their immune systems (immunosuppressive drugs), including people who have received organ transplants, may have an increased risk of anal cancer. HIV — the virus that causes AIDS — suppresses the immune system and increases the risk of anal cancer.

What type of food causes anal canal cancer?

No particular type of food has been shown to increase the risk of anal canal cancer.

To reduce your risk of anal cancer:

  • Practice safe sex: Practicing safe sex may help prevent HPV and HIV, two sexually transmitted viruses that may increase your risk of anal cancer. If you choose to have anal sex, use condoms.
  • Get vaccinated against HPV. A vaccine to protect against HPV infection is available. It's recommended for adolescents, including both boys and girls, but maybe given to adults, too.
  • Stop smoking. Smoking increases your risk of anal cancer. Don't start smoking. Stop if you currently smoke.


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