Mucosal melanomas are non-cutaneous malignant melanomas arising from mucosal epithelium.
This article is an overview; for specific locations in the body, see their respective articles: sinonasal mucosal melanoma.
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Epidemiology
Mucosal melanomas are rare, comprising about 1% of all melanomas 1. The median age of diagnosis is 70 years, higher than that of cutaneous melanomas 2. There are no known environmental risk factors.
Pathology
Etiology
The histogenesis of melanomas, including mucosal melanomas, is from melanocytes.
Location
Mucosal melanoma can arise from any mucosal epithelium in the body. The most common locations are the following 1:
- head and neck (55%), most commonly sinonasal, followed by oral cavity
- anorectum (24%)
- female genital tract (18%)
- urinary tract (3%)
Macroscopic appearance
Up to 40% of mucosal melanomas are amelanotic, meaning the tumors are at least partially devoid of the melanin pigment 2.
Staging
Staging system differs depending on the primary site of disease 2. Head and neck tumors are staged by the American Joint Committee on Cancer TNM system. Melanomas of the external lip and vulva are staged as cutaneous melanomas. Anorectal and vaginal tumors do not have a specifically designed staging system but can be categorized by the following system originally introduced by Ballantyne for the head and neck 3:
- stage I: clinically localized disease
- stage II: regional lymph node involvement
- stage III: distant metastases
Radiographic features
MRI
T1 hyperintensity is characteristic, reflecting melanin, but not universal, likely due to amelanosis 4.
Treatment and prognosis
Treatment typically consists of surgical excision and radiation therapy. Decisions for systemic chemotherapy are based on limited evidence, often extrapolated from cutaneous melanoma. The prognosis is poor, with a five-year overall survival of 25% 1.
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