Mucosal Melanoma: Mechanisms of Its Etiology, Progression, Resistance and Therapy

Mucosal melanoma (MM) is a rare, aggressive cancer whose incidence has increased continuously over the years. This subtype of melanoma arises from melanocytes on hairless surfaces, typically in the respiratory tract, gastrointestinal (GI) tract, and urogenital tract. The most common sites of occurrence include the head and neck, the anorectal region, and the vulvovaginal region, while the rare sites of MM are the urinary tract and the upper and lower GI tract, including the esophagus, duodenum and the gallbladder. MM arises in melanocytes of the ectodermal mucosa that originate from neural crest cells and migrate through embryonic mesenchyme to their destination. Although melanocytes are located mainly in the epidermis and dermis, their presence in various extracutaneous sites, such as the eyes, mucosal tissue, and leptomeninges, is known. Although both cutaneous melanoma (CM) and MM differ in their epidemiology, genetic profile, and clinical presentation, their treatment options are similar. In contrast to the higher treatment response of CM, MM is characterized by a lower response rate to available treatment options, resulting in a poorer survival rate. In this review, we provide an overview of the biology of MM and the mechanisms regulating its development, progression and treatment resistance.