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What Is a Subungual Melanoma?

Medically Reviewed by Melinda Ratini, DO, MS on June 23, 2021

Subungual melanoma is a serious type of skin cancer that occurs in the skin under your nails. 

Subungual melanomas are rare, seen in only 0.07% to 3.5% of the people in the world who have melanoma. But these melanomas can spread to other parts of your body and cause death. Because they are so rare and life-threatening, it is important to learn how to identify subungual melanomas and get treatment as early as possible. 

Causes

The exact cause of subungual melanomas is unknown. Researchers do know, however, that this type of melanoma is different from others because it has no connection to sun exposure. 

Symptoms

In 75% to 90% of reported cases, subungual melanomas have been found in the thumb and the big toe. But they can be seen in other toes and fingers. And they can be quite painful.

Subungual melanomas usually look like brown-black discolorations in the nail bed. The discoloration may be in the form of a long, thin line, or streak, or it can be irregularly shaped. The discolored section of the nail can get thicker, split, or become damaged in some other way, to the point where it can’t be repaired.‌

Inflammation, a normal bodily process that fights infection or injury, can also be present. Chemicals released by the abnormal tissue cause your white blood cells to start the repairing process. Sometimes the inflammation itself can become serious, putting your health at risk. 

Risk Factors

Researchers have seen that among African American, Asian, and Hispanic populations, when a melanoma that is not typical presents itself, it is often a subungual melanoma. Still, the occurrences are rare in general. 

Subungual melanomas have been seen in 75% of African, 25% of Chinese, and 10% of Japanese people who have been diagnosed with melanoma. They most typically affect women in their 60s and men in their 70s.  ‌‌  

Doctors use the following factors to determine whether a nail discoloration is a subungual melanoma:  

  • ‌You are between 50 and 70 years of age and are African, Asian, or Native American in origin.‌
  • ‌You have a brown-black colored band on your nail that is larger than three millimeters in size with irregularly shaped edges.
  • The discoloration grows, and at what rate it does so.
  • It's in the nail bed of your thumb, big toe, or index finger, although it can be seen in other fingers and toes.
  • It shows the "Hutchinson sign," that is, it spreads from the nail bed to the area around it. 
  • You have a family history of melanoma.

Diagnosis

‌Your doctor will initially do a clinical examination of the affected area and review your medical history. Your doctor may also want to know what medications you are taking, if any, and may ask about your family medical history. ‌

Your doctor may want you to go through a dermatoscopy/dermascopy, a noninvasive (without insertion of instruments) procedure to find out how serious your condition is. Or they may want to carry out a full-thickness biopsy to confirm subungual melanoma. In a biopsy, a sample of the suspect tissue is taken and viewed under a microscope.

When to See a Doctor

‌You should see a doctor as soon as you suspect you have a subungual melanoma. More generally, visit your doctor when you see a fingernail or toenail that:

  • Has dark streaks
  • Is starting to lift up from the nail bed
  • I‌s surrounded by redness and swelling
  • Has a greenish-black hue
  • ‌Shows pitting: tiny marks that look like they’ve been made by an icepick
  • ‌Turns yellowish
  • ‌Has deep grooves or gaps
  • L‌ooks thick and overgrown
  • Looks thin and spoon-shaped
  • Looks like you have been picking at or pulling back on the cuticle, the skin at the bottom of your nail
  • L‌ooks curved
  • Has any other type of unusual coloring

Treatment

At one time, doctors preferred to surgically remove, that is, amputate, the affected toe or finger.  But there are other options now. Your doctor may choose to: 

  • Remove only the abnormal tissue.
  • U‌se radiotherapy, treatment through X-rays.
  • ‌Use immunotherapy, in cases of metastatic melanoma. Metastatic melanoma is when your cancer spreads to other parts of the body. Immunotherapy is a treatment that helps your own body's immune system fight the cancer.

Amputation is still a possibility for the worst cases. 

Outlook

Be aware of the signs of subungual melanoma so you can get early treatment. If your condition is diagnosed early and medically managed, the chances of you successfully surviving it are high.  ‌

If you get treatment soon after the condition shows up, at Stage IA, the survival rate is 97% at five years, and 95% at 10 years. The survival rates can get lower depending on how advanced the condition is when diagnosed and treated. If subungual melanoma is diagnosed at its final stage, or Stage IV, the survival rate is 15% to 20% at five years and 10% to 15% at 10 years.

WebMD Medical Reference

Sources

SOURCES:

American Academy of Dermatology Association: "12 NAIL CHANGES A DERMATOLOGIST SHOULD EXAMINE." 

Australian Family Physician: "Pigmented lesions of the nail bed – Clinical assessment and biopsy." 

Cancer Research UK: "What is radiotherapy?" 

Mayo Clinic: "Melanoma," "Nutrition and healthy eating." 

Mole, R., MacKenzie, D. Subungual Melanoma, StatPearls Publishing, 2021.  

National Cancer Institute "Immunotherapy to Treat Cancer." 

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