If moles exhibit irregular borders, color changes, or grow rapidly, it may indicate melanoma, a deadly form of skin cancer. Any unusual changes in moles should prompt immediate medical evaluation. Early detection and treatment are crucial for successful outcomes in skin cancer cases. Regular skin checks are essential for early detection of abnormalities.


Melanoma is a kind of skin cancer that starts in the melanocytes. Melanocytes are cells that make the pigment that gives skin its color. The pigment is called melanin.

Melanoma typically starts on skin that’s often exposed to the sun. This includes the skin on the arms, back, face and legs. Melanoma also can form in the eyes. Rarely, it can happen inside the body, such as in the nose or throat.

The exact cause of all melanomas isn’t clear. Most melanomas are caused by exposure to ultraviolet light. Ultraviolet light, also called UV light, comes from sunlight or tanning lamps and beds. Limiting exposure to UV light can help reduce the risk of melanoma.

The risk of melanoma seems to be increasing in people under 40, especially women. Knowing the symptoms of skin cancer can help ensure that cancerous changes are detected and treated before the cancer has spread. Melanoma can be treated successfully if it is found early.



The first melanoma signs and symptoms often are:

  • A change in an existing mole.
  • The development of a new pigmented or unusual-looking growth on the skin.

Melanoma doesn’t always begin as a mole. It also can happen on otherwise healthy skin.

Melanomas symptoms can happen anywhere on the body. Melanomas most often develop in areas that have had exposure to the sun. This includes the arms, back, face and legs.

Melanomas also can happen in areas that aren’t as exposed to the sun. This includes the soles of the feet, palms of the hands and fingernail beds. Melanoma also can happen inside the body. These hidden melanomas are more common in people with brown or Black skin.

Typical moles

Typical moles are generally a uniform color. They might look pink, tan, brown or black. In people with brown and Black skin, typical moles are more likely to be dark brown or black. Typical moles have a distinct border separating the mole from the surrounding skin. They’re oval or round and usually smaller than 1/4 inch (about 6 millimeters) in diameter.

Most moles begin appearing in childhood and new moles may form until about age 40. By the time they are adults, most people have between 10 and 40 moles. Moles may change in appearance over time and some may even go away with age.

Signs that may indicate melanoma

Some moles aren’t typical. They may have certain characteristics that indicate melanomas or other skin cancers. Characteristics may include:

  • Asymmetrical shape. Look for moles with unusual shapes, such as two very different-looking halves.
  • Changes in color. Look for growths that have many colors or unusual color patterns.
  • Changes in size. Look for new growth in a mole larger than 1/4 inch (about 6 millimeters).
  • Changes in symptoms. Look for changes in symptoms, such as new itchiness or bleeding.
  • Unusual border. Look for moles with unusual, notched or scalloped borders.

Moles that become cancers can all look very different. Some may show all of the changes listed above, while others may have only one or two unusual characteristics.

Hidden melanomas

Melanomas also can develop in areas of the body that have little or no exposure to the sun. These areas may include the spaces between the toes and on the palms, soles, scalp or genitals. These are sometimes referred to as hidden melanomas because they occur in places most people wouldn’t think to check. When melanoma occurs in people with brown or Black skin, it’s more likely to occur in a hidden area.

Hidden melanomas include:

  • Melanoma inside the body. Mucosal melanoma develops in the mucous membrane. This tissue lines the nose, mouth, esophagus, anus, urinary tract and vagina. Mucosal melanomas are especially difficult to detect because they can easily be mistaken for other far more common conditions.
  • Melanoma in the eye. Eye melanoma also is called ocular melanoma. It most often occurs in the layer of tissue beneath the white of the eye. This layer is called the uvea. An eye melanoma may cause vision changes and may be diagnosed during an eye exam.
  • Melanoma under a nail. Acral-lentiginous melanoma is a rare form of melanoma that can occur under a fingernail or toenail. It also can be found on the palms of the hands or the soles of the feet. Acral-lentiginous melanoma tends to be very dark, flat and have very unusual borders. It’s more common in people of Asian descent and people with brown or Black skin.

When to see a doctor

Make an appointment with your doctor or other healthcare professional if you notice any skin changes that worry you.