Melanoma is a serious type of skin cancer that develops in the cells that produce melanin, which is the pigment that gives skin its color. Melanoma may also form in the eyes, nose and throat.


Signs of melanoma include a change in an existing mole and the development of a new pigmented or unusual-looking growth on the skin. However, melanoma doesn’t always begin as a mole; it may occur on skin that appears normal.


Normal Moles vs. Moles Indicating Melanoma

Normal moles are tan, brown or black and have a distinct border separating the mole from the skin. Normal moles are oval or round and usually no bigger than ¼ inch wide.

New moles may form in individuals under age 40, with most adults having between 10 and 40 moles. Over time, moles may change in appearance and even disappear.

Characteristics of unusual moles that may indicate melanoma are:

  • Asymmetrical shape, such as two very different-looking halves
  • Irregular border, such as notched or scalloped
  • Changes in color or an uneven distribution of color
  • Increased diameter, such as larger than ¼ inch
  • Evolving shape, size or color
  • New signs and symptoms, such as itching or bleeding

Individuals with darker skin are more likely to develop melanoma in a hidden area that receives little to no exposure to the sun. Hidden areas may include the spaces between the toes and on the palms, scalp, soles and genitals.

Melanoma may also occur:

  • Under a nail. This is called acral-lentiginous melanoma; also found on the palms of the hands or the soles of feet; more common in Asian and black individuals and those with dark skin color
  • In the mouth, urinary tract, digestive tract or vagina. This is called mucosal melanoma; occurs in the mucous membrane that lines the mouth, nose, esophagus, anus, urinary tract and vagina; difficult to detect and often mistaken for other more common conditions.
  • In the eye. This is called eye melanoma or ocular melanoma; occurs in the uvea, which is the layer beneath the white of the eye; may cause vision changes; may be diagnosed during an eye exam.

Risk Factors

Exposure to ultraviolet (UV) rays from sunlight or tanning beds may increase a patient’s risk of developing melanoma.

The following factors may increase an individual’s risk of developing melanoma:

  • Having fair skin, blond or red hair and light-colored eyes
  • Easily developing freckles or sunburn
  • History of sunburn
  • Living close to the equator or at a higher altitude
  • Having many moles (over 50 ordinary moles) or unusual moles
  • Family history of melanoma
  • Weakened immune system

Diagnosing Melanoma

During an initial visit, the physician will perform a physician exam and look for signs of melanoma. The physician may also perform a biopsy by removing a sample of tissue from a suspicious area. The sample is examined in a lab and tested for melanoma.

If melanoma is diagnosed, then the physician will take the following steps to determine the cancer’s stage:

  • Measure the thickness of the tumor; the thicker the tumor, the more serious the condition.
  • Perform a sentinel node biopsy to see if the melanoma has spread to the lymph nodes.
  • Recommend imaging tests to see if the cancer has spread to other areas of the body.