How is melanoma diagnosed?

If you have a mole or other spot that looks suspicious, your doctor may remove it and look at it under the microscope to see if it contains cancer cells. This is called a biopsy.

Once diagnosed, melanoma will be categorized based on several factors, such as how deeply it has spread and the appearance under the microscope. Tumor thickness is the most important characteristic in predicting outcomes.

Melanomas are grouped into the following stages:

  • Stage 0 (Melanoma in situ): The melanoma is only in the top layer of skin (the epidermis).
  • Stage I: Low-risk primary melanoma with no evidence of spread. This stage is generally curable with surgery.
  • Stage II: There are features indicating higher risk of recurrence but there is no evidence of spread.
  • Stage III: The melanoma has spread to nearby lymph nodes or nearby skin.
  • Stage IV: The melanoma has spread to more distant lymph nodes or skin or has spread to internal organs.

Some patients may need a biopsy of nearby lymph nodes to determine if the melanoma has spread. This is called sentinel lymph node biopsy. Other necessary tests may include a chest X-ray, a computed tomography (CT) scan, a magnetic resonance imaging (MRI) scan, a positron emission tomography (PET) scan, and blood work.

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