Anal cancer is a rare disease, affecting over 1,400 people a year in the UK. It is more common in women than in men.
The anus (back passage) is the 4cm long end portion of the large bowel, which opens to allow solid waste to exit the body. Abnormal changes of the anus are sometimes harmless in their early stages, but may go on to develop into cancer. Different cancers can develop in different parts of the anus. Types of anal cancer include:
Squamous cell carcinomas
The most common type of anal cancer is squamous cell carcinoma, which starts in the cells lining the anal margin and the anal canal. The anal margin is the edge of the anus that can be partly seen as darker skin on the outside of the body and the anal canal is the part of the anus that is inside the body. The earliest stage of squamous cell carcinoma is known as carcinoma in situ, or Bowen’s disease.
An estimated 20% of anal cancers are called adenocarcinoma. These affect glands in the anal area and one type of adenocarcinoma that can occur in the anal area, known as Paget’s disease, can also affect the vulva, breasts, and other areas of the body. Anal adenocarcinomas are usually treated in the same way as rectal cancer.
Skin related cancers
A small number of anal cancers are either basal cell carcinomas, or malignant melanomas –two different types of skin cancer.
Other types of anal cancer
Other, very rare types of anal cancer are lymphomas, and gastrointestinal stromal tumours (GIST).
Anal cancer causes and risk factors
We don’t know what causes most anal cancers, but several factors may increase your risk of developing the disease.
You are more at risk of getting anal cancer if you have one or more of the following risk factors:
- The most common risk factor is Human papilloma virus (HPV), an infection which causes genital and anal warts.
- A history of cervical or vaginal cancer, or abnormal cells of the cervix, likely to be linked with HPV or smoking.
- A lowered immune response as a result of another condition or treatment for other illnesses which suppress your immune system, such as HIV, or following organ transplantation.
- Smoking tobacco has been shown to increase the risk of developing many cancers, including cancer of the anus.
- Being aged over 50, and in younger adults with HIV infection.
- Some data suggests that people with a high lifetime number of sexual partners, are at higher risk. This may be due to the increased risk of contracting HPV.
Symptoms of anal cancer
The symptoms of anal cancer are very similar to other problems, including haemorrhoids (piles) or anal fissures (tears). The most common symptom is rectal bleeding or blood in the stools (poo), with almost half of all patients affected in this way.
Other symptoms include:
- Small lumps seen or felt around the anus which could be confused with piles
- An increase in the number or size of piles
- Pain in the anal area – affects about 30% of people
- Difficulty in passing stools and extreme constipation are common symptoms
- Feeling a continuous urge to pass a motion, with no production, possibly with increased mucus
- Discharge from the back passage, or swelling, itching and persistent redness or soreness around the anal area
- Difficulty controlling your bowels (faecal incontinence)
- One or more lumps in the groin area.
Updated August 2018. Due for review March 2019.