Anal cancer

Anal cancer is a type of cancer that develops in the tissues of the anus or the lining of the anal canal. The anal canal is the short tube that connects the anus (the opening) to the rectum (the lower part of the digestive system). While anal cancer is rare, the majority of cases are of squamous cell carcinomas (American Cancer Society, 2025). It is essential to be aware of the different types, risk factors, and symptoms associated with this condition.

What is Anal Cancer?

Anal cancer, also known as carcinoma of the anal canal, is a type of cancer that develops in the tissues or lining of the anal canal. The anal canal is the connection between the anus (the opening) and the rectum (the lower part of the digestive system). Anal cancer can occur in different parts of the anus and is often categorised based on the type of cell where the cancer originated. Understanding the different types of anal cancer is crucial for accurate diagnosis and effective treatment.

There are several types of anal cancer, each with its own characteristics and treatment approaches:

• Squamous cell carcinoma: Squamous cell carcinoma is the most common type of anal cancer. It develops from the flat, scale-like cells called squamous cells that line the anal canal and the skin around the anus. Squamous cell carcinomas grow slowly and can often be treated successfully if caught early.

• Adenocarcinoma: Adenocarcinoma is a less common type of anal cancer that arises from the glandular cells in the lining of the anal canal. These cells are responsible for producing mucus. Adenocarcinomas of the anus are often treated similarly to rectal cancers due to their shared characteristics.

• Basal cell carcinoma: Basal cell carcinoma is a type of skin cancer that can develop in the perianal skin, which is the skin around the anus. Although it is rare in this location, it is treated in the same way as basal cell carcinomas found elsewhere on the body, typically with surgical removal.

• Melanoma: Melanoma is a serious type of skin cancer that can rarely occur in the anal region. It develops from the pigment-producing cells called melanocytes. Anal melanomas are often more aggressive and harder to treat compared to other types of anal cancer, partly because they are often diagnosed at a later stage.

• Small cell cancer: Small cell cancer is a very rare and aggressive type of anal cancer. It is named after the small, round appearance of the cancer cells under a microscope. Small cell cancers of the anus are treated similarly to small cell cancers found in other parts of the body, typically with a combination of chemotherapy and radiation therapy.

Some of the early signs of anal cancer include:

• Bleeding from the rectum or anus

• Pain in the anal area

• Severe itching (pruritus) around the anus

• A mass or growth in the anal opening

• Mucus or pus discharge from the anus

• Changes in bowel habits, such as difficulty controlling bowel movements or more frequent, looser stools

Anal cancer can present various symptoms that may resemble those of other conditions. Common symptoms include:

• Bleeding: Unexplained bleeding from the anus or rectum is a common symptom and may occur during bowel movements. This bleeding can also be noticed in the stool itself.

• Pain or discomfort: Persistent pain or discomfort in the anal region is often reported by patients. This pain may worsen during bowel movements or while sitting.

• Lump or mass: The presence of a lump or mass near the anus can indicate anal cancer. This abnormal growth may feel hard and can be alarming when noticed.

• Changes in bowel habits: Patients may experience changes such as narrowing of the stool, diarrhoea, or constipation. These alterations can signal an underlying issue that requires attention.

• Itching or irritation: Persistent itching or irritation around the anus is another symptom to watch for. This discomfort is often accompanied by inflammation in the area.

• Narrowing of the anal canal: Narrowing of the anal canal can occur due to a tumour obstructing the passage. This may lead to difficulty with bowel movements and discomfort.

• Unexplained weight loss: Significant weight loss without changes in diet or activity can be concerning. This symptom may indicate that the body is fighting an underlying health issue.

The National Cancer Institute (2025) has provided the following anal cancer staging, which helps determine the extent of the disease and guides treatment decisions. The stages are:

• Stage 0: Also known as carcinoma in situ, in this stage, cells are found in the mucosa (innermost layer) of the anus. These abnormal cells may become cancerous and spread into nearby normal tissue. Stage 0 is also called a high-grade intraepithelial lesion (HSIL).
• Stage 1: The cancer is 2 cm or smaller and has not spread to lymph nodes or distant sites.
• Stage 2: The cancer is larger than 2 cm but has not spread to lymph nodes or distant sites.
• Stage 3: The cancer is any size and has spread to nearby lymph nodes but not to distant sites.
• Stage 4: The cancer has spread to distant lymph nodes or other parts of the body. Stage IV anal cancer is also called metastatic anal cancer.

Anal cancer is linked to several risk factors and causes that can contribute to its development. Key factors include:

• Human papillomavirus (HPV) infection: A significant number of anal cancer cases are associated with HPV, particularly high-risk strains (type 16 and 18). This sexually transmitted virus can lead to abnormal cell growth in the anal area.
• Age: The risk of developing anal cancer increases with age. Most cases are diagnosed in individuals over 50 years old.
• Weakened immune system: Individuals with compromised immune systems, such as those with HIV/AIDS or those on immunosuppressive medications, are at higher risk. This weakened immunity can hinder the body's ability to fight off infections like HPV.
• History of anal or cervical dysplasia: Previous diagnoses of anal or cervical dysplasia indicate abnormal cell growth, which may increase the risk of developing anal cancer. Regular monitoring is essential for individuals with such histories.
• Smoking: Cigarette smoking has been linked to an increased risk of anal cancer. The harmful substances in tobacco can damage DNA and promote cancer development.
• Sexual practices: Certain sexual practices, particularly receptive anal intercourse, may increase the risk of HPV infection and subsequent anal cancer. Engaging in unprotected sex can also heighten this risk.
• Chronic anal inflammation: Conditions that cause chronic inflammation in the anal area, such as anal fistulas or inflammatory bowel disease, may contribute to the risk of anal cancer. Persistent irritation can lead to changes in cell structure.

Certain factors can increase your risk of developing anal cancer, including:

• Age (particularly after 50 years)

• History of cervical, vulvar, or vaginal cancer

• Chronic immunosuppression, such as in people with HIV/AIDS or organ transplant recipients

• Smoking

• Multiple sexual partners

• History of anogenital warts

• Chronic anal fistulas or open wounds in the anal area

• Human papillomavirus (HPV) infection

Anal cancer can lead to various complications that may affect both physical health and quality of life. Key complications include:

• Metastasis: Anal cancer can spread to nearby lymph nodes and other distant organs, such as the liver or lungs. This progression can complicate treatment and worsen prognosis.

• Bowel obstruction: As the tumour grows, it can obstruct the anal canal or rectum, leading to difficulties with bowel movements. This may result in severe pain, constipation, and the need for surgical intervention.

• Fistulas: The development of anal fistulas, which are abnormal connections between the anal canal and surrounding skin, can occur due to tumour growth or infection. This condition may require surgical repair and can lead to discomfort and drainage issues.

• Radiation therapy complications: Radiation therapy may result in skin damage, anal canal narrowing from scarring, anal or rectal ulcers, diarrhoea, urgency to have bowel movements, faecal incontinence, bladder inflammation, and small bowel blockages.

• Chemotherapy complications: Chemotherapy commonly causes nausea, vomiting, diarrhoea, hair loss, reduced bone marrow function, lung inflammation or scarring, and changes in hand and foot nerve function.

Preventing anal cancer involves addressing several key risk factors and making lifestyle changes. These include:

• HPV vaccination: Vaccination against human papillomavirus (HPV) is strongly recommended for both males and females. The vaccine protects against high-risk HPV types, particularly HPV-16 and HPV-18, which are closely linked to the development of anal cancer.

• Lifestyle changes: Making certain lifestyle modifications can significantly reduce the risk of anal cancer. Quitting smoking is vital, as smoking is a major risk factor.

• Safe sexual practices: Engaging in safe sex can lower the risk of contracting HPV and HIV infections. This includes reducing the number of sexual partners and avoiding receptive anal sex, which is associated with a higher likelihood of these infections.

• Management of HIV: For individuals living with human immunodeficiency virus (HIV), adhering to antiretroviral therapy is crucial. This helps maintain immune system health, which can potentially reduce the risk of developing anal cancer.

Diagnosing anal cancer involves a combination of physical examinations, imaging studies, and biopsies to confirm the presence of cancer and assess its stage. These include:

• Medical history and physical examination: The diagnostic process typically begins with a thorough review of the patient’s medical history, including symptoms and risk factors. A digital rectal exam is performed, where the doctor inserts a gloved, lubricated finger into the rectum to feel for any abnormal growths or lumps.
• High-resolution anoscopy (HRA): If suspicious areas are detected, the doctor may recommend a high-resolution anoscopy (HRA). During this procedure, a magnifying instrument is used to closely inspect the anal canal, allowing for a detailed examination and the collection of tissue samples (biopsies) for laboratory analysis. HRA with targeted biopsy is considered the gold standard for detecting and diagnosing anal lesions (Cohen and Clarke, 2023).
• Biopsy: Biopsy samples are essential for confirming the presence of cancerous cells. The pathologist analyses these samples to identify the specific type of anal cancer, such as squamous cell carcinoma, adenocarcinoma, or melanoma.
• Computed tomography scan: A computed tomography (CT) scan may be ordered to evaluate the extent of the cancer and check for metastasis to nearby lymph nodes or other organs.
• Magnetic resonance imaging: Magnetic resonance imaging (MRI) can provide detailed images of the anal region and surrounding tissues, helping to assess the tumour's size and location.
• Positron emission tomography scan: A positron emission tomography (PET) scan may be utilised to identify areas of cancer spread throughout the body, aiding in staging the cancer.
• Ultrasound: In some cases, an ultrasound may be performed to evaluate the depth of the cancer's invasion into the anal sphincter muscles. This information is valuable for determining the best treatment approach.

The treatment of anal cancer is tailored based on factors such as the stage of the disease, tumour size, lymph node involvement, and the patient’s overall health and preferences. A multidisciplinary approach is typically adopted, combining chemotherapy, radiation, surgery, and, in select cases, newer targeted or immunotherapy options.

1. Chemoradiotherapy

Concurrent chemoradiotherapy forms the cornerstone of anal cancer treatment. It combines chemotherapy and radiation therapy to enhance tumour control, preserve sphincter function, and reduce the need for surgery.

• Fluorouracil (5-FU): It is an antimetabolite that disrupts DNA synthesis, used to enhance the effect of radiation and improve tumour eradication.
• Mitomycin: It is a DNA crosslinking agent that acts as a radiosensitiser, increasing the cancer-killing potential of radiation.
• Capecitabine: It is an oral prodrug of 5-FU, often used as an alternative for its convenience and similar efficacy when combined with radiation.

3. Chemotherapy

In addition to its use with radiation, chemotherapy is employed in advanced, metastatic, or recurrent anal cancer cases.
Common regimens include:

• Cisplatin and  Fluorouracil (5-FU): It is a platinum-based combination used for locally advanced disease, recurrent cases, or when first-line chemoradiotherapy fails.
  Carboplatin + Paclitaxel: This combination is considered in metastatic disease or as salvage therapy, particularly when cisplatin-based regimens are not tolerated.

4. Surgery

Surgery is generally reserved for situations where chemoradiotherapy has failed or when there is persistent or recurrent disease.

• Abdominoperineal Resection (APR): Removal of the anus, rectum, and part of the sigmoid colon, typically accompanied by a permanent colostomy. This is considered when there is a residual or recurrent tumour not amenable to further chemoradiotherapy.
  
   

Living with anal cancer involves navigating both physical and emotional challenges. Here are a few points to consider:

• Managing side effects from chemotherapy and radiation, such as skin irritation, pain in the anal area, fatigue, chemotherapy-induced cognitive impairment, nausea, and vomiting, is a crucial aspect of anal cancer treatment.

• For those undergoing surgery, especially those requiring a permanent colostomy, significant lifestyle adjustments are necessary.

• Support from healthcare teams, including stoma nurses, is essential to helping patients adapt to these changes.

• Patients may also benefit from joining support groups or seeking counselling to help cope with the emotional and psychological impact of the disease.

• Regular follow-up appointments are crucial to monitor for any signs of recurrence and to address any ongoing side effects or complications.

If you are experiencing symptoms that could indicate anal cancer, it is crucial to seek medical attention promptly. Rectal bleeding, even if minor, should always be evaluated by a doctor. Other symptoms that warrant medical attention include persistent anal pain or discomfort, changes in bowel movements, anal irritation or discharge, and the presence of a lump or mass at the anal opening. Unexplained weight loss or other systemic symptoms should also be brought to your doctor's attention.

• Anal cancer is a rare but serious form of cancer that affects the tissues of the anus.

• Risk factors for anal cancer include human papillomavirus (HPV) infection, smoking, immunosuppression, and chronic inflammation of the anal region.

• Early signs of anal cancer may include rectal bleeding, itching, pain, or lumps in the anal area.

• The primary treatment for anal cancer is chemoradiation, which combines chemotherapy and radiation therapy.

• Surgery may be necessary for salvage therapy or in cases of recurrent or advanced disease.

• Regular follow-up and monitoring are essential for detecting recurrence and managing side effects.

• Patients should seek medical attention if they experience any new or worsening symptoms related to anal cancer or its treatment.