Can dark stripes under fingernail indicate melanoma skin cancer? Fact Check

A message spreading online claims that a women attending a nail clinic was told to see her doctor after the nail technician noticed a black line running down her fingernail, which turned out to be a form of skin cancer known as melanoma.

TRUE

An example of the message spreading online can be read below.

I had a walk-in nail client a couple weeks ago. She had been going to the “NAILS” type salons for years. She had a straight dark vertical stripe down her nail. She said as soon as she sat down—I need a color dark enough to cover this stripe. The nail salons “diagnosed” her a few different ways. Some said it was a lack of calcium. Some said it was hereditary. At least one had told her it was a blood blister.
This is melanoma!!! I did not want to frighten her but I told her she needed to see her doctor immediately! She called me today to tell me that yes it was a very aggressive melanoma that has already spread to her lymph nodes!! Her prognosis is not good!Please pay attention to abnormalities in your nail beds!! Odd changes in your nails can very likely be nothing to worry about! But sometimes it is an indication of a very serious disease. And please keep an eye on the nail beds—toes and fingers—-of your elderly loved ones and your loved ones that aren’t physically able to notice changes in the nail beds! Early diagnosis can make all the difference in the world!!!

The post appears to have been originally authored by nail technician Lisa Harrison Williams back in 2017, and there is little reason to doubt the specific anecdote since a dark line in the fingernail can indeed be a symptom of melanoma. However it should also be noted that dark patches or stripes (called linear melanonychia) under the fingernail can also be caused by a variety of other, less serious issues.

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The NHS website noted that dark stripes running down the nails is “fairly common”, especially in black people over the age of 20.

Dark stripes running down the nails (linear melanonychia) are fairly common in black people over 20 years of age, and in most cases it’s perfectly normal.

However the NHS also note that dark stripes should not be ignored…

However, dark stripes shouldn’t be ignored because it can sometimes be a form of skin cancer that affects the nail bed, called subungual melanoma. It’s important that your doctor checks it to rule out melanoma.

Other causes of melanonychia can include “physiologic longitudinal melanonychia, systemic disorders, trauma, inflammatory disorders, fungal infections, drugs, and benign melanocytic hyperplasias.”

Other social media users have pointed out that the condition can also be a harmless hereditary condition.

To summarise, if you have dark patches or stripes under your fingernail that you can’t explain, see your doctor, since the condition can have a number of different causes ranging from serious to perfectly harmless, and it is always prudent to have a specialist check it out for you.