Anal cancera disease where abnormal cells split without control and spread to other nearby body tissue and/or organs is a rare malignancy that develops in the anusthe opening where solid waste (faeces or stool) exits the body, which is the opening where solid waste (faeceswaste product from the bowel sent to the anus for removal; also known as stool or poo or stoolwaste product from the bowel sent to the anus for removal; also known as faeces or poo) exits the body. It is found at the end of the lower gastrointestinal tract (GI tract).
The lower GI tract is divided into three separate areas: the small bowelportion of the digestive system that digests food (small bowel) and absorbs salts and water (large bowel); also called intestines, the large bowel and the anus. The small bowel receives food from the stomach and absorbs the nutrients from the food, and is comprised of three separate parts (the duodenum, jejunum and ileum). The food is then passed onto the large bowel, where water and salts are absorbed. The large bowel also consists of three parts (the caecum, colonthe longest portion of the large bowel that absorbs water and salts from ingested food and rectumthe last section of the large intestine/bowel that holds waste until it is ready to be removed from the body). What is left over is turned into solid waste (faeces or stool), and is sent to the anus to be removed from the body.
The anus is made up of two distinct regions: the anal canal, and the anal margin. The anal canal is the 4cm portion at the end of the large bowel that leads to the anal opening. This region is surrounded by two ring-shaped sphincter muscles, which are responsible for controlling the release of faeces from the body. The anal margin is the skin that internally surrounds the anal opening, and lies between the anal canal and the perianalarea surrounding the anus skin (which is the skin surrounding the outside of the anal opening).
Anal cancer is slightly more common in women, and tends to be diagnosed in people over 50 years of age. However, anyone can develop this disease.
Types of Anal Cancer
There are different types of anal cancer, which are categorized based on the types of cellsthe basic structural and functional unit of all living things the cancer develops from.
Squamous Cell Carcinoma (SCC)
Anal squamous cell carcinomas are the most common type of anal cancer, and develop from the squamous cells that line the anal canal or anal margin. This type of cancer can be aggressive and can metastasise, however, it can have a good prognosisto predict how a disease/condition may progress and what the outcome might be when caught early.
Adenocarcinoma
Anal adenocarcinomas are a less common subtype of anal cancer, and develop from mucus producing cells in the anal canal. These types of anal cancers are often treated similarly to bowel cancers. Anal adenocarcinomas can often be aggressive, and may not have as good of a prognosis as other types of anal cancer.
Rare forms of Anal Cancer
These types of anal cancers are very rare:
- Basal cell carcinoma (skin cancer that develops from basal cells in the perianal skin).
- Melanoma (skin cancer that develops from melanocytes in the perianal skin).
- Gastrointestinal stromal tumours (a type of sarcomacancer arising from bones and/or soft tissue that develops from the lining of the gastrointestinal tract).
- Anal lymphomacancers of the lymphatic system (a very rare cancer often appearing as a type of non-Hodgkin lymphoma).
Treatment
If anal cancer is detected, it will be staged and graded based on size, metastasiswhen the cancer has spread to other parts of the body, also known as mets, and how the cancer cells look under the microscope. Stagingthe process of determining how big the cancer is, where it started and if it has spread to other areas and grading helps your doctors determine the best treatment for you.
Cancers can be staged using the TNM staging system:
- T (tumoura tissue mass that forms from groups of unhealthy cells) indicates the size and depth of the tumour.
- N (nodea small lump or mass of tissue in your body) indicates whether the cancer has spread to nearby lymph nodessmall bean-shaped structures that filters harmful substances from lymph fluid.
- M (metastasis) indicates whether the cancer has spread to other parts of the body.
This system can also be used in combination with a numerical value, from stage 0-IV:
- Stage 0: this stage describes cancer cells in the place of origin (or ‘in situ’) that have not spread to nearby tissuea group of cells that work together to perform a function.
- Stage I: cancer cells have begun to spread to nearby tissue. It is not deeply embedded into nearby tissue and had not spread to lymph nodes. This stage is also known as early-stage cancer.
- Stage II: cancer cells have grown deeper into nearby tissue. Lymph nodes may or may not be affected. This is also known as localisedaffecting only one area of body cancer.
- Stage III: the cancer has become larger and has grown deeper into nearby tissue. Lymph nodes are generally affected at this stage. This is also known as localised cancer.
- Stage IV: the cancer has spread to other tissues and organs in the body. This is also known as advancedat a late stage, far along or metastatic cancer.
Cancers can also be graded based on the rate of growth and how likely they are to spread:
- Gradea description of how abnormal cancer cells and tissue look under a microscope when compared to healthy cells I: cancer cells present as slightly abnormal and are usually slow growing. This is also known as a low-grade tumour.
- Grade II: cancer cells present as abnormal and grow faster than grade-I tumours. This is also known as an intermediate-grade tumour.
- Grade III: cancer cells present as very abnormal and grow quickly. This is also known as a high-grade tumour.
Once your tumours have been staged and graded, your doctor may recommend genetic testinga procedure that analyses DNA to identify changes in genes, chromosomes and proteins, which can be used to analyse tumour DNA to help determine which treatment has the greatest chance of success, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment is dependent on several factors, including location, age, stage of disease and overall health.
Treatment options for anal cancers may include:
- Radiation therapya treatment that uses controlled doses of radiation to damage or kill cancer cells.
- Chemotherapya cancer treatment that uses drugs to kill or slow the growth of cancer cells, while minimising damage to healthy cells.
- Surgerytreatment involving removal of cancerous tissue and/or tumours and a margin of healthy tissue around it to reduce recurrence, potentially including:
- Wide local excisionremoval of cancerous tissue and a margin of healthy tissue around it to prevent cancer recurrence.
- Abdominoperineal resectionsurgical removal of the anus, rectum and a portion of the sigmoid colon through an incision in the abdomen.
- Clinical trialsresearch studies performed to test new treatments, tests or procedures and evaluate their effectiveness on various diseases.
- Palliative carea variety of practices and exercises used to provide pain relief and improve quality of life without curing the disease.
Risk factors
While the cause of anal cancer remains unknown, the following factors may increase the likelihood of developing this disease:
- Having been infected with the human papillomavirus (HPV).
- Having a weakened immune system, potentially due to:
- Having the human immunodeficiency virus (HIV).
- Having recently had an organ transplanta surgical procedure that involves removing a failing or damaged organ and replacing it with a healthy one from a donor.
- Having an autoimmune disease, such as coeliac disease, lupus, or Grave’s disease.
- Having unprotected anal sex.
- Having multiple sexual partners.
- Having anal or genital warts.
- Having a personal history of vulvar, vaginal and/or cervical cancer.
- Having a history of smoking.
Not everyone with these riskthe possibility that something bad will happen factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
Symptoms
In the early stages of disease, people with anal cancer may appear asymptomatic. As the cancer progresses, some of the following symptoms may appear:
- Anal/rectal bleeding.
- Bloodthe red bodily fluid that transports oxygen and other nutrients around the body in stool or on toilet paper.
- Bowel changes, such as incontinenceloss of control over release of urine or faeces.
- Mucousal discharge from the anus.
- Pain, itching, pressure, and/or discomfort around the anus.
- A lump near the anus.
- Ulcers around the anus.
- Feeling of fullness, discomfort, and/or pain in the rectum.
Not everyone with the symptoms above will have cancer but see your general practitioner (GP) if you are concerned.
Diagnosis
If your doctor suspects you have anal cancer, they may order the following tests to confirm the diagnosisthe process of identifying a disease based on signs and symptoms, patient history and medical test results and refer you to a specialist for treatment:
- Physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Digital rectal examinationan examination conducted by a urologist where a finger (or digit) is inserted into the rectum to feel the anus (DRE).
- Imagingtests that create detailed images of areas inside the body tests, potentially including:
- MRI (magnetic resonance imaging)a type of medical imaging that uses radiowaves, a strong magnet and computer technology to create detailed images of the body.
- CT (computed tomography) scana type of medical imaging that uses x-rays and computer technology to create detailed images of the body.
- TRUS (transrectal ultrasound)a type of ultrasound that involves inserting a device (known as a transducer) into the rectum to produce sound waves and create images of the rectum, prostate gland and surrounding tissues in greater detail; also known as an endorectal ultrasound.
- Blood teststesting done to measure the levels of certain substances in the blood.
- Endoscopya procedure that involves inserting a long, flexible tube with a light and small camera (endoscope) into the body to view internal organs, potentially including a proctoscopyexamination of the rectum and anus with a small, flexible instrument called a proctoscope .
- Biopsyremoval of a section of tissue to analyse for cancer cells.
