Melanoma is a very common skin cancer that concerns solely melanocytes, cells that lie in the skin’s epidermis, the middle layer of eye (iris, retina), in the inner ear (cochlea, stria), the digestive epithelium (tissue that lines the inside of the large and small intestine), and the meninges. Melanocytes play many roles in your body, among them pigmentation of skin and hair. Melanoma occurs when, due to certain pathogenic factors (see risk factors), some of these cells multiply uncontrollably to form a malignancy.
Intense or excessive sun exposure, especially in childhood, is the main factor responsible for the development of melanoma. This risk is even higher if you have fair skin. Although people with white skin are more often victims of melanoma, the cancer can also affect individuals with dark or pigmented skin. In black people, the cancer develops particularly on the palms (of hands) and soles (of the feet).
Depending on the characteristic of the cancer, melanoma is divided into many stereotypes; the most common include:
- Superficial spreading melanoma (SSM) – SSM represent about 70% of melanomas; it is the most common form of cutaneous melanoma in the lighter-skinned populations. Often developed on the sun-exposed skin areas, a mole of superficial spreading melanoma tends to growhorizontally for several months or years before taking its vertical extension where the lesion becomes thick and nodular.
- Nodular melanoma (NM) – the lesion of this form of melanoma tends to grow vertically. Due to its rapidity to grow, nodular melanoma is often considered as the most aggressive form of melanoma. It is characterized by a small blue-black or flesh colored spotting lump. Nodular melanoma lesions tend to penetrate deeper into the skin and bleed easily.
- Acral lentiginous melanoma – also known as subungual melanoma, acral lentiginous melanoma develops mostly on the palms, soles and under the nails. Unlike many forms of melanoma, acral lentiginous melanoma is more frequent among black and Asian people, and can develop on any area of the body which may or may not be exposed to sunlight. Acral melanoma is characterized by brown spot, flesh-colored nodules, which tends to resemble a wart or spotting tumor.