Is a Black Spot on the Toenail Cancerous?

Hi, my name is Weilan Johnson, and I am a board-certified dermatologist at U.S. Dermatology Partners. Today I’m going to talk to you about black spots in our toenails.
Often patients will come to see us for concern for black spots in either toenails or fingernails. One concern that patients may have when they have black spots on the toenails or fingernails is, “Is this a skin cancer?” Oftentimes, the most common cause of black spots in the toenails or fingernails is actually a bruise or hemorrhage under the toenail. Some patients will remember the trauma that brings this on but it's most concerning to patients when they don't remember the type of trauma that brings it on but believe it or not it is still the most common cause is some forgotten trauma that causes a slight bruise in our fingernail or toenail.
When we get a bruise in our fingernail or toenail, it's unlike bruises in our skin that will resolve over two to three weeks on their own. Sometimes when we get bruises in our toenail and there's blood underneath the skin or the fingernail or toenail it can actually stain the nail so that it doesn't resorb like a normal bruise would. Often, patients have to wait sometimes several months for that stain or bruise to grow out of the toenail or fingernail. A patient should be concerned about having a black spot in their toenail or fingernail if number one: they don't remember any trauma that could have caused it and that that black spot is not growing out as the fingernail or toenail grows. Another concerning feature would be if that black spot continues to grow and grow and grow. If it stays stable and grows out that's a reassuring feature. If this black spot continues to grow and get bigger or if it starts to involve the skin around the nail called the cuticle, if it involves the skin around the nail that's another concerning feature. Also, if there's any bleeding from the fingernail or toenail then that would be another concerning feature. Certainly, if there is a dark line in the fingernail or toenail something that generally we like to evaluate. Sometimes these can be normal but other times it can be a sign of cancer involving the nail unit so that's definitely something if you have a dark line or ridge in your nail that we would like to evaluate in person.
If you have a concern with any dark spots in your fingernails or toenails, you can visit our website at USDermatologyPartners.com and find a location nearest you.