Introduction:
Anorectal melanoma is an abnormal tissue growth in the mucosa of the anus or rectum. The rectum is a passage in the back through which the digestive waste is excreted from the body. The symptoms of anorectal melanoma are pain or itching in the anus or the rectum, a mass in the anus or rectum, changes in bowel habits, and constant feeling to poop (excretion). It is diagnosed with a few tests like rectal examination, imaging studies, and biopsy. Then, anorectal cancer is surgically removed, and other treatments like chemotherapy and radiation therapy are also recommended.
What Is Anorectal Melanoma?
Anorectal melanoma is a cancerous (spreads to other parts) tissue growth in the lining of the anus or rectum. It is a rare and aggressive form of cancer. The anus is the external opening through which the digestive waste products called stools are excreted from the body. The rectum is the last part of the large intestine that holds the digestive waste, which is transferred from the colon before moving to the anus.
Melanoma is the cancer of a cell called melanocytes. It gives color to the skin. If the melanocytes are present large in number, they provide a brown or black color to the skin. The mucosa is a soft lining in the inner part of many organs and structures like the mouth, esophagus (food pipe), intestine, anus, and rectum.
What Causes Anorectal Melanoma?
The exact reasons for anorectal melanoma are unclear. However, studies by New et al. reveal mutations in specific gene expression cause anorectal melanoma.
What Are the Stages of Anorectal Cancer?
The cancer staging shows if the cancer is spread to other organs and if the tumor size is increased.
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Stage I or Local: The cancer is present in the anus and rectum alone and has not spread to other parts.
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Stage II or Locally Advanced: Cancer has spread to lymph nodes in the groin, which is the nearest structure.
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Stage III or Advanced: Cancer has spread to other body parts like the liver, lungs, or intestine.
What Are the Symptoms of Anorectal Melanoma?
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Pain or itching in the anus.
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Mass felt in the anus.
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Have a feeling to poop, though the bowel is empty.
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Unexplained weight loss.
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Changes in bowel habits like constipation or incontinence and diarrhea.
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Lump in the groin (a part of the hip between the thigh and the stomach).
What Are the Tests Done to Find Out Anorectal Melanoma?
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Rectal Examination: The doctor examines the rectum with a gloved hand to check for any lumps in the rectum.
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Vaginal Examination: Female patients are usually subjected to vaginal examination. Since the anus and vagina are located nearby, an internal examination of the vagina is done. The doctor examines the vagina with a gloved hand using two fingers to check for any changes in the size or shape of the vagina.
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Computerized Tomography (CT) Scan: Computerized tomography imaging techniques use high-frequency radio waves from different angles to capture images of the organs on a computer. It gives a detailed appearance of the organ or the structure.
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Magnetic Resonance Imaging (MRI) Scan: Magnetic resonance imaging scan uses high-frequency sound waves in a magnetic field to capture images of the internal organs. It gives a detailed view of the organ and soft tissues.
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Positron Emission Tomography: PET-CT (positron emission tomography computerized tomography) is performed using a radiotracer material like fluorine-18. The radiotracer is injected into the patient and detects the cancer cells in the body.
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Endorectal Ultrasound: Endorectal ultrasound is used to detect abnormalities in the rectum. A thin probe is inserted into the rectum, which releases high-energy sound waves to capture images of the internal part of the rectum.
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Endoscopy: A thin, adjustable tube with a light and camera is inserted into the rectum to view the changes in the rectum or the presence of a lesion. It is also used for obtaining biopsy samples.
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Groin Ultrasound: A high-energy sound wave is used to capture the soft-tissue images of the groin.
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Fine Needle Aspiration of Lymph Nodes: A small part of the tissue from the lymph node is removed with a needle and syringe to view the tissues in a microscope. It is a confirmatory test that reveals if the cancer is spread to the lymph nodes (a part of the immune system that filters substances in the lymphatic vessels and fights against disease and infections).
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Biopsy: A tiny portion of the lesion is removed to view the changes on a microscopic level. It is a confirmatory test and reveals the type of tumor.
How Is Anorectal Melanoma Treated?
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Surgery: The first choice of treatment for anorectal cancer is the surgical removal of the tumor. The tumor's local surgical excision is done if the staging is the stage I. Surgical resection (removing a layer of the mucosa and the lesion) is performed in stage II cases.
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Chemotherapy: Anti-cancer drugs like Dacarbazine, in addition to high-dose interferon and interleukin-2, are recommended. It targets and kills cancer cells.
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Radiation Therapy: A high dose of radiation is targeted at cancer, and the cells are damaged. It is an additional treatment with other management procedures.
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Targeted Therapy: Ipilimumab is a medication that boosts the immune system and blocks the action of cytotoxic T-lymphocyte-associated antigen (CTLA-4) and programmed death protein (PD1). The cytotoxic T-lymphocyte-associated antigen (CTLA-4) and programmed death protein (PD1) are responsible for immunosuppression (inactivates the immune system) of immune checkpoints (immune system regulators).
What Is the Prevalence of Anorectal Melanoma?
Anorectal melanoma can occur in age. It is commonly seen in people above 60 years. It is more prevalent in females than males, and the reasons are unclear.
What Is the Prognosis of Anorectal Melanoma?
Patients with anorectal melanoma have a poor prognosis. The five-year survival rate of anorectal patients is around 4.3 % to 17.4 %. The median survival rate is about 21 months.
Conclusion:
Anorectal melanoma is aggressive cancer growth in the anus or the rectum. It tends to spread at a rapid rate. The symptoms like mass in the rectum, pain in the rectum, unexplained weight loss, and changes in bowel habits occur. They are accurately found with a rectal examination, imaging techniques, and biopsy. The melanoma is surgically removed, or a layer of the rectal mucosa is removed with the tumor. Anorectal melanoma has a poor survival rate, and if the condition is detected at a late stage, cancer may spread to other organs, and treatment becomes challenging. Although anorectal melanoma is rare and violent, early diagnosis and treatment will prolong the patient's lifespan.
