Mucosal melanoma

Author: Debra Yeh, Medical Student, University of Auckland, New Zealand; Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, April 2014.

What is mucosal melanoma?

Melanoma develops if there is uncontrolled growth of melanocytes, the cells responsible for pigmentation. The majority of melanomas are cutaneous, ie they grow within the skin.

Mucosal melanoma is a rare type of melanoma that occurs on mucosal surfaces. Mucous membranes are moist surfaces that line cavities within the body. This means that mucosal melanoma can be found in the respiratory tract, gastrointestinal tract or genitourinary tract.

Mucosal melanomas are most often found in the head and neck, in the eyes, mouth, nasopharynx and larynx, but they can also arise throughout the gastrointestinal tract, anus and vagina. They make up approximately 1.1% of all melanomas but are usually more complicated because of late diagnosis due to their less visible locations and because they are often amelanotic – meaning they are not pigmented.

Which parts of the body are affected by mucosal melanoma?

Subtypes of mucosal melanoma are based on the tissue in which they arise. Melanoma can start within any mucosal epithelium. The most common sites are:

Who gets mucosal melanoma?

The peak age of diagnosis of mucosal melanoma is between 70 and 79. However, younger people have also been known to develop mucosal melanoma, especially of the oral cavity.

Mucosal melanoma of the genital tract is more common in females.

What causes mucosal melanoma?

While there are many suggested risk factors for mucosal melanoma, there is only weak evidence for all, and none that are widely accepted. About 25% of mucosal melanomas have been linked with problems with a gene called KIT. Genes are the templates used for making protein, and mutations in the KIT gene cause the production of a mutant protein. The KIT gene can also be over-expressed, which means that there is more of the KIT protein being made than usual. Both the mutation and over-expression of the KIT gene have been associated with mucosal melanoma.

Possible risk factors include:

Oral mucosal melanoma

Vulvar melanoma

Anorectal melanoma

Signs and symptoms of mucosal melanoma

The signs and symptoms of mucosal melanoma largely depend on its location. Therefore, there are a wide variety of symptoms that patients may experience.

Mucosal melanoma of the head and neck

Vulvovaginal melanoma

Anorectal melanoma

What testing is done in mucosal melanoma?

If there is suspicion of mucosal melanoma, the most important test is a biopsy of the involved tissue. If the pathology report indicates melanoma, the patient will be fully examined and further tests may be undertaken to find out if it has spread further. These may include:

Staging of mucosal melanoma

Head and neck mucosal melanoma

The American Joint Committee on Cancer (AJCC) Tumour, Node, and Metastasis (TNM) classification is used to stage mucosal melanoma of the head and neck. Mucosal tumour staging begins at T3 (advanced). Like cutaneous melanoma, mucosal melanoma can also spread to lymph nodes or through the blood stream to other areas of the body. Here, they can form new tumours. These are referred to as metastases.

Primary Tumour
T3 Mucosal disease
T4a Moderately advanced disease. Tumour involving deep soft tissue, cartilage, one, or overlying skin.
T4b Very advanced disease. Tumour involving brain, dura, skull base, lower cranial nerves (IX, X, XI, XII), masticator space, carotid artery, prevertebral space or mediastinal structures
Regional lymph nodes
NX Regional lymph nodes cannot be assessed
N0 No regional lymph node metastases
N1 Regional lymph node metastases present
Distant metastasis
M0 No distant metastasis present
M1 Distant metastasis present
Clinical stage
Stage III T3 N0 M0
Stage IVA T4a N0 M0
T3-T4a N1 M0
Stage IVB T4b Any N M0
Stage IVC Any T Any N M1
AJCC-TNM classification for mucosal melanoma of the head and neck

Vulvovaginal mucosal melanoma

Vulval melanomas are staged using the same AJCC-TNM classification as the table above. There is no staging system for vaginal melanoma, so a simplified clinical staging system can be used to categorise these melanomas.

Vaginal melanoma
Stage I Clinically localised disease
Stage II Regional nodal involvement
Stage III Distant metastatic involvement

Anorectal mucosal melanoma

Anorectal mucosal melanoma is staged using the same simplified staging system as vaginal melanoma.

Anorectal mucosal melanoma
Stage I Clinically localised disease
Stage II Regional nodal involvement
Stage III Distant metastatic involvement

Treatment of mucosal melanoma

The best form of treatment for mucosal melanoma is wide local excision of the lesion. This may not always be possible, as the melanoma may be located on an important anatomical structure, or be too large to excise safely.

Due to the likelihood of the same melanoma recurring, surgical resection is often combined with radiotherapy. Radiotherapy is also a consideration for patients who are not suitable for surgery.

Prognosis of mucosal melanoma

Mucosal melanomas have a poor prognosis, as most patients develop metastases despite aggressive therapy.

Type of mucosal melanoma5-year survival rate*
Head and neck 12-30%
Vulvovaginal Vulval 24-77%
Vaginal 5-25%
Anorectal 20%

*The 5-year survival rate refers to the percentage of patients that survive for at least 5 years after their diagnosis, and is approximate.

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