12 Signs of Skin Cancer

7. Streaks or bruises in the fingernails or toenails

ALM can also develop as subungual melanomas under the fingernails or toenails. An early sign of this type of cancer is a dark stripe under the nail, usually the big toe or the thumb. As the streak grows, the nail may crack or break. Doctors may misdiagnose the condition as a fungal infection or a trauma injury, delaying accurate identification. Interestingly, the streaks that appear under the fingernail or toenail of people with darker skin are usually benign but should still be evaluated.