What Is Anorectal Melanoma?
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Anorectal Melanoma: Causes, Diagnosis, and Treatment

Published on Jan 20, 2023 and last reviewed on May 26, 2023   -  4 min read


Anorectal melanoma is a rare cancerous growth in the anus or the rectum. Let us know more details about anorectal melanoma in this article.


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.

  • Stage I or Local: The cancer is present in the anus and rectum alone and has not spread to other parts.

  • Stage II or Locally Advanced: Cancer has spread to lymph nodes in the groin, which is the nearest structure.

  • Stage III or Advanced: Cancer has spread to other body parts like the liver, lungs, or intestine.

What Are the Symptoms of Anorectal Melanoma?

  • Pain or itching in the anus.

  • Mass felt in the anus.

  • Have a feeling to poop, though the bowel is empty.

  • Unexplained weight loss.

  • Changes in bowel habits like constipation or incontinence and diarrhea.

  • 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?

  • Rectal Examination: The doctor examines the rectum with a gloved hand to check for any lumps in the rectum.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • Groin Ultrasound: A high-energy sound wave is used to capture the soft-tissue images of the groin.

  • 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).

  • 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?

  • 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.

  • Chemotherapy: Anti-cancer drugs like Dacarbazine, in addition to high-dose interferon and interleukin-2, are recommended. It targets and kills cancer cells.

  • 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.

  • 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.


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.

Frequently Asked Questions


How Is Anorectal Melanoma Staging Done?

Anorectal melanoma is a rare and aggressive form of cancer that develops in the anal canal or rectum. Staging is an important process in cancer diagnosis, which helps determine the extent and spread of the disease. Anorectal staging is based on tumor size, lymph node involvement, distant metastasis, and mitotic rate. Based on the above factors, anorectal melanoma is assigned a stage using the AJCC staging system, ranging from stage I to stage IV.


What Is the Best Cancer Treatment Procedure for Melanoma?

The treatment approach for melanoma, including anorectal melanoma, depends on various factors such as the stage of the cancer. Treatment options like surgery, immunotherapy, targeted therapy, radiation therapy, and chemotherapy. The best treatment procedure for melanoma is highly individualized and should be determined by a multidisciplinary team of healthcare professionals. 


Can Melanoma Be Effectively Cured Without Surgery?

Surgery is typically the primary treatment for localized melanoma and offers the best chance of a cure. It involves removing the tumor and a margin of healthy tissue near it to ensure that all cancer cells are eliminated. These treatment options aim to destroy or eliminate cancer cells without surgical intervention. Non-surgical options include immunotherapy, radiation therapy, and targeted therapy.


How Is Primary Anorectal Melanoma Effectively Treated?

 Primary anorectal melanoma is a rare and fierce form of cancer that originates in the anal canal or rectum. Treatment for primary anorectal melanoma typically involves a combination of surgery, radiation therapy, and sometimes chemotherapy. Some treatment options are surgery, chemotherapy, immunotherapy, and radiation therapy.


What Is a Spindle Cell Melanoma?

Spindle cell melanoma is a rare variant of melanoma, a type of skin cancer that originates from the pigment-producing cells called melanocytes. Spindle cell melanoma is characterized by the presence of spindle-shaped cells within the tumor. This spindle cell melanoma is a relatively rare subtype of melanoma, and the management may differ from typical melanoma.


Is Desmoplastic Melanoma Similar to Spindle Cell Melanoma?

Desmoplastic melanoma and spindle cell melanoma are both subtypes of melanoma, but they have distinct characteristics and clinical behaviors. While they may share some similarities in terms of their cellular appearance, they are considered separate entities.


Is Amelanotic Melanoma a Malignant Condition?

Yes, amelanotic melanoma is a malignant condition. Amelanotic melanoma refers to a subtype of melanoma where the tumor cells do not produce the pigment melanin. Melanin is responsible for the dark color commonly associated with melanoma. It can be more challenging to diagnose compared to other types of melanoma because it may lack typical visual cues, such as dark or discolored lesions. It can present as a flesh-colored, pink, or red bump, or even as a non-healing ulcer or a scar-like area.


Is Anorectal Melanoma a Curable Condition?

Anorectal melanoma is a rare and aggressive form of cancer that occurs in the anal canal or rectum. Its prognosis and potential for cure depend on various factors, including the stage of cancer at diagnosis, the extent of spread, and the individual's overall health. When the tumor has metastasized to lymph nodes or distant areas, the prognosis becomes progressively less certain. The response to treatment and long-term outcomes can vary significantly depending on the individual case.


Is Anorectal Melanoma a Hereditary Condition?

Anorectal melanoma is not typically considered a hereditary condition. While some types of melanoma can have a hereditary component, such as familial atypical mole and melanoma syndrome (FAMM), which is caused by specific gene mutations, anorectal melanoma is not commonly associated with inherited genetic factors.


Can an Individual Survive Anorectal Melanoma?

The likelihood of survival in cases of anorectal melanoma can differ based on various factors such as the stage of cancer upon diagnosis, the presence of metastasis, the efficacy of treatment, and the individual's overall health. It is usually diagnosed at an advanced stage due to its location and the nonspecific nature of early symptoms. The delayed diagnosis can limit treatment options and impact survival rates. Overall, a five-year survival rate for anorectal melanoma is relatively low, typically ranging from 20% to 40%.


At What Age Does Anorectal Melanoma Occur?

Anorectal melanoma tends to occur at any age, but it is mostly diagnosed in older individuals. The median age at diagnosis for anorectal melanoma is around 60 to 70 years old. While anorectal melanoma is more commonly seen in older individuals, it can still occur in younger adults and even in rare cases in children and adolescents. It is necessary for all individuals despite of age to be aware of the potential signs and symptoms of anorectal melanoma and to seek medical attention.


What Is Anorectal Melanoma Stage 3?

The staging of anorectal melanoma adheres to TNM staging, which considers factors such as tumor size and infiltration, lymph node participation, and the existence of distant metastasis. Stage three anorectal melanoma is divided into subcategories, including stage 3A, stage 3B, and stage 3C. In this stage, the tumor has invaded the deeper layers of the anal canal, with no distant metastasis.


What Is the First Site of Melanoma Metastasis?

The first site of melanoma metastasis can vary from person to person. Melanoma has the potential to spread (metastasize) to various organs and tissues in the body. The specific sites of metastasis and their order of occurrence depend on various factors, including the stage of the melanoma, the characteristics of the tumor, and individual patient factors.


Can Melanoma Have a Tendency to Cause Colon Cancer?

Melanoma and colon cancer are two distinct types of cancer that arise from different cell types and have different risk factors. While they are both categorized as cancers, there is no direct causal relationship between melanoma and colon cancer. Melanoma originates from melanocytes, which are pigment-producing cells primarily found in the skin, while colon cancer develops in the cells lining the colon or rectum.

Last reviewed at:
26 May 2023  -  4 min read




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