Lifestyle

Moles That Change Shape or Color Can Be an Early Sign of Melanoma. The Warning Signs Dermatologists Look For

By Erica Coleman · October 30, 2026

Most adults have plenty of moles, and most of them are harmless. The one worth watching is the mole that starts to look different.

Melanoma is a skin cancer that starts in melanocytes, the cells that make the pigment that gives skin its color. According to Mayo Clinic, the first sign of melanoma is often a mole that changes size, shape or color. The other common early sign, it says, is a new pigmented or unusual-looking growth on the skin. Melanoma doesn’t always begin as a mole and can also appear on otherwise healthy skin.

For comparison, Mayo Clinic says typical moles are generally one uniform color, have a distinct border, are oval or round, and are usually smaller than about a quarter inch across. Most adults have between 10 and 40 of them.

To help people spot trouble, dermatologists created the ABCDEs of melanoma, according to the American Academy of Dermatology. These are the warning signs it lists.

A is for asymmetry. One half of the spot is unlike the other half.

B is for border. The spot has an irregular, scalloped or poorly defined edge.

C is for color. The spot has varying colors from one area to the next, such as shades of tan, brown or black, or areas of white, red or blue.

D is for diameter. Melanomas are usually larger than 6 millimeters, about the size of a pencil eraser, when diagnosed, though they can be smaller.

E is for evolving. The spot looks different from the rest or is changing in size, shape or color.

A spot does not need to show every sign. Mayo Clinic says some cancerous moles show all of these changes while others have only one or two unusual features.

The academy lists other ways melanoma can look, including a spot that resembles a new mole, freckle or age spot but looks different from others on the skin; a firm, dome-shaped growth that may look like a sore and may bleed; a dark brown or black vertical line beneath a fingernail or toenail; and a slowly growing patch of thick skin that looks like a scar. It also flags a sore that doesn’t heal or heals and returns.

Melanoma is often painless. The academy says many people feel no discomfort, and for many the only sign is a spot with some of the ABCDEs. Sometimes it can itch, hurt or bleed. Mayo Clinic advises talking to a doctor about any change in the color or size of a mole, or if itching, pain, bleeding or inflammation develops.

Melanoma can also form in places that get little sun. Mayo Clinic lists the soles of the feet, the palms and the nail beds, and says these hidden melanomas are more common in people with brown or Black skin.

Mayo Clinic says most melanomas are caused by ultraviolet light from sunlight or tanning lamps and beds. It lists risk factors that include a family history of melanoma, a history of severe blistering sunburns, having more than 50 moles or unusual moles, and skin that burns or freckles easily. It also says melanoma can be treated successfully if it is found early.

That makes regular skin checks worthwhile. The academy recommends a skin self-exam as often as your dermatologist advises and seeing a board-certified dermatologist for any spot with the ABCDEs. Mayo Clinic suggests using mirrors to check the face, neck, ears and scalp, and checking the soles of the feet and the spaces between the toes.

This article is for general information and is not medical advice. See a doctor or dermatologist about any new or changing spot on your skin. This article was produced with the assistance of AI and fact-checked against the sources cited by LightWave Reports.