Cancer Research UK / Wikimedia Commons

What is Melanoma?

Skin Cancer 101: What is Melanoma?

Written By: SERO Board-Certified Physicians

Cancer Research UK / Wikimedia Commons

3D rendering of a melanoma cell. (Cancer Research UK / Wikimedia Commons)

Melanoma is the most dangerous form of skin cancer.

Melanoma is a type of skin cancer caused by damage to the DNA of melanocyte cells in the skin. Melanocytes produce melanin, a pigment in skin that is primarily responsible for skin color. When the cell’s DNA is damaged, it may cause it to mutate—leading to rapid, uncontrolled growth and the formation of malignant tumors.

While melanoma is the least common type of skin cancer, accounting for 135,000 new diagnoses per year in the United States (only 2% of all skin cancer cases), it is also the most serious.

Melanoma is considered highly curable when caught in its earliest stages, before the disease has spread. However, if not identified and treated quickly, melanoma may spread to other areas of the body, including distant organs.

If melanoma spreads (a condition called invasive melanoma) it may become difficult or impossible to cure. In these cases, melanoma can be fatal.

According the the American Cancer Society:

  • An estimated 135,000 new cases are diagnosed in the U.S. every year.
  • In 2015, an estimated 73,870 invasive melanomas were diagnosed, with about 42,670 in males and 31,200 in females.
  • 9,940 people in the U.S. die from melanoma every year.

What are melanocytes?

melanoma diagram

A diagram of melanocytes in the skin. (Public domain image.)


Human skin is made up of a handful of different types of cells. Each type serves a different role in the normal functioning of the skin.

Melanocytes are found in the deepest part of the top layer of skin, called basal layer. They account for 5 to 10% of the cells in the basal layer.


Through a biochemical process called melanogenesis, melanocytes produce melanin. Melanin is a pigment that creates color in the skin, eyes, and hair.

Signs and Symptoms of Melanoma

Melanoma lesion.

Melanoma lesion on a patient’s skin. Public domain image.

Where Melanoma Forms

Melanoma frequently forms on areas of the skin that receive frequent exposure to UV light from the sun, such as the back, legs, arms, and face, but may occur anywhere on the body, including palms, soles of the feet, and underneath fingernails.

Rarely, melanoma can form in parts of the body other than the skin, such as the mouth, eyes, or intestines.

Beware of Moles

A melanoma lesion frequently looks like a mole in its earliest stages. Melanomas often appear as black or brown splotches, but may also be pink, white, blue, or purple. While melanoma often looks like a mole, it may also form as normal-looking skin that is sore, sensitive, or itchy.

Normal moles

Moles are a normal part of skin for many people. Most people have between 10 and 50 on their body. Since many melanomas form from existing moles, it’s important to check your skin every few months and to know the signs of melanoma should they appear.

Characteristics of normal moles include:

  • Uniform color (often black, brown, or skin-colored)
  • Clearly defined edges with a distinct border between the surrounding skin
  • A round or oval shape
  • A diameter no larger than 1/4 inch, or roughly the size of a pencil eraser

Signs of Melanoma

melanoma diagram

Diagram showing where melanoma is most likely to develop.
(Cancer Research UK / Wikimedia Commons)

Melanoma lesions may form suddenly, or may evolve from existing moles. While melanoma can take on many different forms, the general warning sign is a changing or atypical mole.

Consult a doctor if you notice changes in your skin. These may include:

  • The sudden appearance of new moles or growths
  • Moles that change in size over time (exceeding 1/4 inch)
  • Asymetrical moles
  • Moles with uneven borders
  • Moles that change in color
  • Moles that begin to itch, bleed, or become sore.

Causes and Risk Factors of Melanoma

Long-term exposure to UV rays, or specific incidences of brief, intense exposure resulting in severe, blistering sunburns, are believed to be the most common cause of melanoma. Both sunlight and UV rays from tanning beds may cause damage. However, as with all cancers, melanoma is likely the result of both environmental and genetic factors.

The following characteristics may put you at greater risk of developing melanoma:

  • History of severe, blistering sunburn
  • Fair skin. People with less melanin in their skin, those with light-colored eyes and blonde or red hair, and those with freckles, have less built-in protection from UV radiation and are at greater risk of developing melanoma.
  • Frequent sunburns in early childhood
  • Family history of skin cancer, especially melanoma
  • Having a large number of moles (more than 50) or having atypical moles
  • Weakened immune system, caused by medical conditions such as HIV/AIDS, or medical treatments such as chemotherapy

To learn more about melanoma, including treatment options, contact a SERO physician by filling out the contact form in the sidebar, or by calling us at (704) 380-0730.