Many melanomas have some abnormal manifestations in the process of early malignant transformation. When the following seven characteristics of moles on the body appear, it is necessary to seek timely medical attention: 1. Asymmetry: one half of the pigmented mole looks asymmetrical with the other half; 2. Irregular edges: the edges are irregular or have cut marks or jagged teeth, unlike normal pigmented moles that have smooth round or oval outlines; 3. Color change: normal pigmented moles Usually monochromatic, while melanoma mainly shows dirty black, but also can have many different colors such as brown, brown, brown-black, blue, pink, black or even white; 4. Diameter: Pay attention when the diameter of pigment spots is larger than 5-6mm or when the pigment spots grow up. Melanoma is usually larger than ordinary moles, so keep an eye on pigmented moles with a diameter larger than 5mm. It is better to do excisional biopsy for pigmented nevi larger than 1cm in diameter; 5. Bulging: Some early melanomas have a slight bulging of the whole tumor body; 6. Growth rate: Some pigmented nevi that have not changed for many years happen to increase significantly within a few weeks or months; 7. Pigmented nevi that have been growing hair on them suddenly fall off, or break down and do not heal easily.