Whether a nail mother nevus requires treatment should be judged based on the specific circumstances of the nevus. A nail nevus is a striped nevus that grows under the nail and commonly presents clinically as a black line under the nail. A nail nevus has a small tendency to become malignant and may turn into a malignant melanoma. If a patient has a nail mother nevus, he or she can visit a dermatologist and decide whether treatment is needed by observing its appearance, such as color, size, symmetry and smoothness, after being judged by the doctor. If the nevus has symmetrical periphery, uniform color, smooth edges as well as size less than three millimeters, surgery can be temporarily avoided and regular observation can be done. However, if the mole is larger than three millimeters and the periphery of the mole is asymmetrical, the edges are not smooth and the color is not uniform, it often indicates the possibility of cancer and it is recommended to go to the hospital for biopsy. If the test is malignant, it needs to be removed surgically as soon as possible and with subsequent anti-tumor treatment.