What is melanoma?

Melanoma care with Northwestern Medicine Dermatology

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.

What normal skin looks like

Moles are benign (non-cancerous) collections of melanocytes grouped together. Under healthy conditions, the growth of melanocytes is regulated.

A mole and what the cells look like

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.

What melanoma could look like and the cells

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.

picture of acral melanoma

Acral (nails/hands/feet) melanoma

example of Mucosal Melanoma

Mucosal (oral, sinonasal, gastrointestinal tract, anal or vaginal) melanoma

Uveal Melanoma example

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).