You might think skin cancers only appear in areas of the body most obviously exposed to the sun --like the nose or ears, for example. While many skin cancers do commonly occur in such areas, the deadliest kind -- melanoma -- can show up under a nail. Known as acral lentiginous melanoma, the kind of melanoma found under nails is the only skin cancer that is more common in African Americans and Asians than it is in Caucasians in the U.S. [source: Skin Cancer Foundation].
Acral lentiginous melanoma usually appears as dark lines underneath the nail, so if you notice this symptom, see your doctor right away. This type of skin cancer is known to advance quickly.
Another tip: If you get an annual skin cancer check by a dermatologist, be sure to remove any nail polish before showing up for your visit. This will allow the doctor to check your fingernails and toenails for signs of melanoma.