Most melanomas are present in the skin. However, mucosal melanomas occur in the mucous membranes, such as the eyes, mouth, gastrointestinal tract, anus, or vagina.

Melanoma is a type of skin cancer that can be severe due to its ability to spread. It can be challenging to treat, and the outlook for people with melanoma may be poor.

Melanoma can develop when cells grow uncontrollably and cause pigmentation. However, mucosal melanomas do not always have pigmentation and are rare, accounting for about 1.5% of all melanomas.

This article examines mucosal melanoma, its causes, and its signs and symptoms. We also discuss diagnosis, treatment, and outlook for people with mucosal melanoma.

Close up of eyeShare on Pinterest
Jonathan Knowles/Getty Images

Melanoma can develop when the cells responsible for pigmentation, called melanocytes, grow uncontrollably. Most melanomas are cutaneous, meaning they grow in the skin.

Mucosal melanoma is a rare form of melanoma present on mucosal, moist surfaces that line cavities in the body. They are often amelanotic, meaning they do not have any pigment as with other melanomas. Due to this and their hard-to-see locations, people with mucosal melanomas often seek treatment late, which can cause complications and make them more challenging to treat.

Mucosal melanoma can affect any mucosal epithelium, which is a type of tissue in glands that lines cavities and hollow organs in the body. It most commonly occurs in the following sites:

  • oral cavity
  • nasal cavity
  • gastrointestinal tract
  • respiratory tract
  • paranasal sinuses
  • genitourinary tract
  • vagina
  • vulva
  • anal canal

Unlike other melanomas, exposure to UV rays does not cause mucosal melanoma.

While there are various potential risk factors for mucosal melanoma, there is weak evidence to support them. Experts have linked around 25% of mucosal melanomas to mutations and over-expression of a protein in the KIT gene. Age may also be a factor, as the average age of people with mucosal melanoma is 70 years.

Risk factors may include:

Vulvar melanoma

  • genetic factors
  • chemical irritants
  • chronic inflammatory disease
  • viral infections

Oral mucosal melanoma

  • inhaling or ingesting carcinogens
  • smoking
  • dentures that do not fit correctly

Anorectal melanoma

Symptoms and signs of mucosal melanoma can differ widely depending on the location but may include:

Vulva or vaginal melanoma

  • discharge
  • itching
  • discoloration of the vulva
  • bleeding
  • a mass
  • pain during or after intercourse

Mucosal melanoma of the head and neck

  • nosebleeds
  • nasal obstruction
  • ulcers
  • a painless lump
  • discoloration in the mouth
  • loss of smell

Anal or rectal melanoma

  • pain in the anus or rectum
  • bleeding
  • a mass
  • changes to usual bowel movements, such as constipation or diarrhea

If a doctor suspects a mucosal melanoma, they may test a biopsy of the tissue involved. If the biopsy shows there is melanoma present, the doctor will perform a full examination and conduct further tests. These may include:

  • further biopsies of the mucosal melanoma
  • MRI scans, CT scans, or both to determine the primary location of the mucosal melanoma
  • PET scans, CT scans, or both to determine the involvement of the lymph nodes and look for any spread of the cancer

The most effective treatment for mucosal melanoma is surgery to excise and remove the melanoma. However, this is not always an option, as the melanoma may be on or near a vital organ or anatomical structure, making it unsafe to operate on.

If the doctor cannot recommend surgery, a person may need chemotherapy, radiation therapy, or both. Alternatively, they may require these therapies following surgery to reduce the likelihood of recurrence.

The outlook for mucosal melanoma is generally poor. This is because the cancer spreads in most people despite aggressive therapy, and people generally seek treatment in its later stages due to the nonvisible locations of mucosal melanomas.

The estimated 5-year survival rates for common types of mucosal melanoma are as follows:

  • vulva melanoma: 24–77%
  • vaginal melanoma: 5–25%
  • head and neck melanoma: 12–30%
  • anal or rectal melanoma: 20%

The earlier a doctor diagnoses a person, the better their outlook. A person should consult a doctor regularly for checkups and seek medical attention if they experience any of the symptoms of mucosal melanoma.

Mucosal melanoma is a rare type of melanoma that occurs in the mucosal membranes of the body, unlike other melanomas which occur in the skin.

Experts do not know exactly what causes mucosal melanoma, but many have linked it to mutations in the KIT gene. Risk factors may include age, genetic factors, smoking, and viral infections.

To diagnose mucosal melanoma, a doctor will likely take a biopsy of the suspected tissue and perform further testing, such as MRI, CT, and PET scans.

The most effective treatment for mucosal melanoma is surgery to remove the melanoma, followed by chemotherapy and radiation therapy.