A doctor may use several tests to diagnose and stage melanoma, including a physical exam, skin tests, and biopsies. Early diagnosis is key to improving your outlook.

Melanoma is an uncommon type of skin cancer that happens when cells in your skin called melanocytes — the cells that give your skin melanin (pigment) — become cancerous.

If you or a healthcare professional suspects melanoma, several tests can help confirm a diagnosis. Other tests can help determine the type of melanoma and how developed the cancer is.

Read on to learn more about the diagnostic procedures used to test for melanoma and what to expect after a diagnosis.

The first-line diagnostic test for melanoma is a physical examination of the skin, including checking markings or moles on your skin that might suggest the presence of cancerous cells.

Cancerous moles have a different appearance than regular moles. While moles are usually flesh-colored or light brown with smooth, circular edges, cancerous moles may be much darker and have jagged edges.

A physical exam may also include looking at the skin on your:

  • palms
  • scalp
  • feet, including your soles and between toes
  • genitals
  • buttocks
  • eyes
  • mouth

ABCDEs of melanoma

You can keep an eye out for the signs of melanoma that doctors look for:

  • Asymmetrical: One half of the mole doesn’t look like the other half.
  • Border: The mole has an irregular border.
  • Color: The mole has varying colors rather than an even color.
  • Diameter: Melanomas are typically more than 6 millimeters (0.25 inches) in diameter.
  • Evolving: The mole’s appearance changes over time.
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To look more closely at your skin, a doctor may use dermoscopy (also called dermatoscopy).

Dermoscopy involves using a dermatoscope, a tool with a powerful magnifying glass that can examine the structures under your skin. A dermatoscope allows doctors to see how deep or widespread melanoma cells might be under the surface.

A doctor may also recommend reflectance confocal microscopy (RCM). This test uses a near-infrared laser to penetrate through the surface of the skin and detect cancerous cells or lesions that might indicate melanoma.

If a doctor believes a mole might be cancerous, they may recommend a biopsy to remove a sample of skin and test it in a laboratory for the presence of melanoma cells.

In a skin biopsy, a doctor removes a piece of your skin and some tissue below the skin to be tested in a laboratory. This test can help confirm a diagnosis of melanoma and help a doctor decide what stage the cancer is in based on the size and thickness of the tumor.

If a doctor is concerned that melanoma has spread, they may recommend a lymph node biopsy. This involves removing a tissue sample, injecting a dye near where your tumor was located to find nearby lymph nodes, and removing the lymph nodes to test them for cancer.

A doctor may be able to determine the type and stage of melanoma from a biopsy report. But they may also order further diagnostic tests for more accurate results.

Options include:

  • Computed tomography (CT): CT scans use powerful X-rays to get detailed images of where cancer may have spread.
  • Magnetic resonance imaging (MRI): MRIs use magnets and radio waves along with an injected substance called gadolinium to get highly detailed, cross-sectional images of your body to find where cancerous cells have spread.
  • Positron emission tomography (PET): PET scans involve injecting radioactive glucose that a scanner can track. This helps doctors detect areas of high chemical activity in your body where diseased or cancerous tissue might be present.

What’s in a melanoma pathology report?

A melanoma pathology report contains the following information:

  • how thick the tumor is
  • how much nearby skin is scarred or inflamed
  • how quickly cancerous cells are dividing
  • how much cancer has spread into nearby lymph nodes or blood vessels
  • whether cancer has spread into nerve or brain tissue
  • how many immune cells are present in your body fighting cancer cells
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The primary treatment for melanoma is surgery to remove tumors, cancerous tissue, and any affected tissues or organs.

Depending on the type and stage of your melanoma, a doctor may also recommend one or more of the following:

  • taking steps to prevent melanoma from growing or appearing in new places, including wearing sunscreen or covering your skin when you’re out in the sun
  • monitoring moles and other growths closely to make sure cancer doesn’t spread or appear anywhere else
  • visiting a doctor or a dermatologist regularly to continue having physical exams and assessing treatment plans
  • starting treatment plans, such as:

Resources for support

Receiving a cancer diagnosis can be difficult. The following organizations offer support resources, including in-person and online support groups:

You can also call the Cancer Support Community Helpline at 888-793-9355.

The American Cancer Society also offers information, tools, and resources regarding melanoma.

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Here are some of the most frequently asked questions about melanoma diagnostic procedures and tests:

Can you detect melanoma with a blood test?

A blood test won’t help a doctor diagnose melanoma. However, a lactate dehydrogenase (LDH) test can help healthcare professionals find out how far cancer has spread and help guide treatment.

What is the best way to detect melanoma?

Dermoscopy and skin biopsies are the most accurate ways to detect melanoma because they directly involve examining the affected tissue.

What are the basic warning signs of melanoma?

The most basic warning sign of melanoma is the appearance of dark, irregularly shaped moles on your chest, legs, neck, or face. These moles also tend to grow or change shape over a short period.

Melanoma is one of the less common skin cancers but also the most aggressive. Early diagnosis can help prevent melanoma from spreading.

Diagnosing melanoma typically begins with a physical exam to look for signs of skin cancer. Dermoscopy and a biopsy can help confirm a diagnosis, but other tests, such as imaging, can help stage melanoma and guide treatment.