A mole is the most common sign of melanoma, but it can appear under a nail as well. Here's what to look for.

September 05, 2017

UK manicurist Jean Skinner is being hailed as a hero after she spotted a sign of skin cancer on a client—and not on the woman's hands, but actually under one of her nails.

The walk-in client had asked Skinner for a color that would cover up a dark, vertical stripe running down the center of her nail, Skinner explained in a Facebook post. But the nail artist immediately recognized the stripe as more than a beauty woe. “I did not want to frighten her, but I told her she needed to see the doctor immediately!” Skinner wrote.

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...

Posted by Jean Skinner on Saturday, August 19, 2017

RELATED: 6 Things Your Dermatologist Wants You to Know About Skin Cancer

Skinner's hunch was correct: The client later called to say she had been diagnosed with melanoma that had already spread to her lymph nodes.

While there are plenty of nail changes that are totally harmless, this type of stripe or streak can be a sign of a kind of melanoma called acral lentiginous melanoma, or ALM. ALM is probably caused by genetic factors, since it usually occurs in places that don't get much exposure to the sun, according to the Skin Cancer Foundation (SCF), such as under nails and on the palms of the hands. Because people tend to shrug off a little nail discoloration, ALM tends to be diagnosed later than other skin cancers, when it's more likely to have spread to other parts of the body.

Melanoma is typically less common among Hispanic, Asian, and African American people, but when they do get melanoma, it’s more likely to be ALM, Cleveland Clinic dermatologist John Anthony, MD, told Health in a prior interview. In fact, musician Bob Marley died of ALM that spread from a dark spot under his toenail. He thought it was from a soccer injury, according to the SCF.

RELATED: Is It a Mole ... or Skin Cancer?

Melanoma is still most likely to begin in a mole on the skin, but it's important to know that this deadly skin cancer can be found anywhere on the body, including in your eyes and on your scalp. You can prevent some skin cancers by always using a broad spectrum sunscreen, but melanoma may also appear on places that you'd never sunburn, including inside your mouth and on the bottoms of your feet.

An experienced dermatologist will inspect all of these areas and more during an annual skin cancer screening, but you should also be on the lookout for any changes. In fact, the Skin Cancer Foundation recommends giving yourself a once-over from head to toe every month.

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"Please pay attention to abnormalities in your nail beds!" Skinner urged on Facebook. "Odd changes in your nails can very likely be nothing to worry about! But sometimes it is an indication of a very serious disease." Next time you're between polishes, take a closer look at your fingernails—and toenails too. Bring up anything that looks off with your dermatologist ASAP.