There are three types of melanoma, cutaneous, mucosal and ocular melanoma.
Cutaneous melanoma is the most common because most melanocytes are found in the skin, especially in areas exposed to the sun. Cutaneous melanoma can be further divided into superficial spreading, nodular, acral lentiginous and lentigo Maligna melanoma. People who have darker skin have lower risk of developing melanoma in the sun-exposed areas, but have similar risk for the development of melanoma on the palms and soles or under the nail beds.
Mucosal melanoma occurs in the mucous membrane of the body, such as the mouse, throat, sinuses, vagina and anus.
More rarely, melanomas can develop in the eyes, called ocular melanoma, or uveal or choroidal melanoma.
Melanoma that spreads to other parts of the body is called metastatic melanoma. It will usually spread first to the surrounding lymph nodes, and then to other organs such as the liver, lungs, bones or brain.
Recently, certain gene mutations that are found in melanomas help further define melanoma at the molecular level. In cutaneous melanoma, the BRAF mutation is the most common type of genetic mutation (approximately 50% of cases), followed by NRAS mutation (approximately 20% of cases). In mucosal and acral melanoma, the most common mutation is the KIT mutation. Whereas in ocular melanoma, the most common mutations are in the GNAQ and GNA11 genes.