Introduction
Anal adenocarcinoma is a cancerous condition that is found in the anus. A long tube at the end of the rectum is called the anal canal, and the opening is called the anus. This is where stool leaves the body. It is a clinically rare condition. Adenocarcinoma of the anal canal constitutes only five percent of the neoplasms in the anorectal region and about two percent in the gastrointestinal region. A neoplasm is a mass of cells that grow and multiply when they should not or do not die when they should die.
What Is Anal Adenocarcinoma?
Anal adenocarcinoma is a rare malignancy that is found in the anus. Malignancy is a cancerous condition where the cells begin to proliferate unconditionally. Anal cancer occurs when the cells in the anal canal grow and multiply abnormally. Based on the type of cells lining the anal canal, it is divided into three; colorectal zone, anal transition zone, and squamous zone. The World Health Organization divides anal adenocarcinoma into three; those arising from the mucosa of the transitional zone, those arising from the anal glands or ducts, and those developing in a setting of chronic anorectal fistula. People suffering from anal adenocarcinoma usually have a high rate of pelvic failure (the pelvic floor diaphragm, urogenital diaphragm, and the pelvic organs fail to function), distant metastasis (spread to distant organs or lymph nodes), and lower survival rates than those having epidermoid carcinoma. Epidermoid carcinoma is a cancer that arises from the squamous cells, while adenocarcinoma is a cancer arising from glandular cells.
The treatment for anal adenocarcinoma includes surgery, chemotherapy, and radiation therapy.
What Are the Causes of Anal Adenocarcinoma?
The exact cause of anal adenocarcinoma is not fully known. Cancer occurs when a genetic mutation turns a normal cell into an abnormal cell or when cell division is uncontrolled. A genetic mutation is a change in the DNA (deoxyribonucleic acid) to produce something different. These cells that proliferate do not die, causing an abnormal mass. These are called tumors and can metastasize to different places.
What Are the Signs and Symptoms of Anal Adenocarcinoma?
The signs and symptoms of anal adenocarcinoma can include;
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Bleeding from the anus or rectum, especially during bowel movements.
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Pain in the anal area.
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Growth in the area.
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Itching in the area.
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A change in the bowel movements (like the frequency, consistency, etc.).
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Leaking stool.
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Having a very frequent urge to use the toilet.
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Abscess in the anal area.
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Spotting.
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Rectal prolapse - A condition where the rectum falls over the anus. This can cause stool incontinence or leaking of the stool.
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Unexplained weight loss.
Who Are at Higher Risk of Anal Adenocarcinoma?
There are certain risk factors associated with the condition. They include;
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Human Papilloma Infection (HPV): It is the most common sexually transmitted disease. Everyone who is infected with the virus may not show symptoms, though some show warts and other skin lesions.
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Immunosuppressants: Medications that stop the immune system from destroying healthy cells.
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Anal Sex: Men and women are at high risk for anal adenocarcinoma through anal sex. Multiple sex partners increase the risk of HPV, HIV (human immunodeficiency virus), and anal cancer.
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Age: Anal cancers are usually seen in people over 55 years of age.
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Smoking: Smoking increases the risk of anal cancer.
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Weak Immune System: Conditions that can weaken the immune system like those who take steroids for an organ transplant.
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Anal Fistula: An anal fistula is an infected opening from the anus to the skin.
How Is Anal Adenocarcinoma Diagnosed?
Early diagnosis of the condition can help to prevent complications. The diagnosis is made with the help of the signs and symptoms exhibited by the patient. This can be confirmed with a biopsy and histological studies. Inguinal lymphadenopathies should be examined as anal adenocarcinoma is aggressive in nature and may have local and distant metastasis. Inguinal lymphadenopathy is the swelling of lymph nodes of the groin or the lower extremities. Other diagnostic methods to find out distant and local metastasis can include
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Endoanal ultrasound (used to check the anatomy of the anal canal).
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Magnetic resonance imaging (MRI) of the pelvic area.
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Computed tomography (CT).
How Is Anal Adenocarcinoma Treated?
There are very limited cases in the medical literature as a whole about anal adenocarcinoma. Hence, it is difficult to point out a standard therapeutic approach for the treatment of the condition.
Radical surgery (abdominoperineal amputation) was the most recommended mode of treatment until the 1990s. An abdominoperineal amputation is a surgery to remove the anus, the rectum, and a part of the colon. This is done with the help of an incision made in the abdomen. A multicenter study in a retrospective manner done in different European countries recommended combined chemoradiotherapy (CRT) as the best treatment for the condition. Radiation therapy was done as a part of the preservation or preventive therapy. The overall survival rate was higher in patients who received combined CRT than those who received radiation therapy alone or surgery alone. Patients who showed inguinal lymphadenopathies exhibited poor prognoses due to distant metastasis.
At present, more experts advise maximizing the local control of the condition, avoiding transanal resection (removing the rectal tumors and surrounding tissues, leaving the anus and sphincter intact), and reducing the risk of distant metastasis with the help of intense chemotherapy.
What Is the Differential Diagnosis for Anal Adenocarcinoma?
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Adenocarcinoma of the lower rectum.
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Hemorrhoids are called piles, swollen veins in the anus and rectum.
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An anal fissure is a small tear in the lining tissue of the anus.
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Anal warts are the presence of warts in and around the anus.
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Fistula-in-ano is an infected tunnel between the anus and the skin.
Conclusion
An anal adenocarcinoma is a rare form of cancer. At times, it is difficult to distinguish between adenocarcinoma of the lower rectum with extensions to the anal canal. It is highly aggressive in nature. Hence, early diagnosis and treatment are very important for a better prognosis. Although there is no standard treatment for the condition, combined CRT is commonly accepted, followed by radical surgery and adjuvant therapy to prevent metastasis. Adjuvant therapy is a treatment given additionally (after the primary treatment of cancer) to prevent recurrence or metastasis.
