It pays to be familiar with the surprising symptoms you'd never normally think were a sign of cancer. A manicurist used her knowledge when one of her clients came in looking for a nail polish that was dark enough to cover a strange mark that had appeared on her nail.On Facebook, Jean Skinner, in an attempt to educate others, uploaded a photograph, with permission, of the woman's nail, which had a clear dark stripe, almost the color of tattoo ink, down the middle of it."I had a walk-in nail client a couple weeks ago," Skinner wrote in 2017. "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 customer informed Skinner that various other salons had previously suggested the mysterious line could have been cause by a number of things, including a calcium deficiency, a blood blister or simply being a hereditary mark with no real explanation.But as Skinner knew, none of the above were the case. The dark line was an indication that her customer had melanoma, a form of skin cancer."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," Skinner wrote. Sadly, she added that her client's prognosis was not good.Urging others to recognize unusual symptoms such as these, the Skinner continued, "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... Early diagnosis can make all the difference in the world."