Melanoma is a cancer of pigment-producing cells known as melanocytes. These cells are evenly distributed throughout normal human skin. Melanocytes produce melanin, which provides the skin with color and protection from ultraviolet (UV) rays of the sun.
Moles are benign (non-cancerous) collections of melanocytes grouped together. Under healthy conditions, the growth of melanocytes is regulated.
Melanoma occurs when the growth of either individual melanocytes scattered throughout the skin or melanocytes in moles become uncontrolled. This results in cancer of the melanocytes.
One-third of all melanomas come from pre-existing moles, while two-thirds are derived from single melanocytes scattered throughout the skin. UV rays are the most significant cause of uncontrolled growth of melanocytes resulting in melanoma. Melanoma can occur anywhere in the body where there are melanocytes. This includes the skin, nails, mucosa and eyes.
Acral (nails/hands/feet) melanoma
Mucosal (oral, sinonasal, gastrointestinal tract, anal or vaginal) melanoma
Uveal (eye) melanoma
These images were published in Pathology of Melanocytic Tumors, Busam, K. J., Scolyer, R. A., & Gerami, P. Figure 14.3(A), Figure 24.13, Figure 23.2, pgs. 170, 267, 275. Copyright Elsevier Health Sciences (2018).
