Melanoma is the “king of cancers”. It has a high degree of malignancy, early metastasis and high mortality. Malignant melanoma is a tumor that arises from melanocytes in the skin and other organs. The disease is highly prevalent in the United States and Australia, and China has the fifth highest incidence in the Asia-Pacific region. However, due to the large base, there are many patients in China. Unlike Australian patients, who tend to occur on the back, statistics have found that 50% of Chinese patients with malignant melanoma occur on the palms of the hands, soles of the feet, and the extremities of the nails, compared to less than 5% of Caucasians. Its etiology remains unclear and may be related to excessive sun exposure, malignant transformation of poorly structured moles, heredity, trauma, endocrine abnormalities, chemical carcinogens, and immunodeficiency or hypoimmune function. Can a mole develop into a tumor? In general, it is unlikely that a pigmented mole will turn into a melanoma, and even if it does develop, it will take a relatively long time. However, if the pigmented nevi in sun-exposed areas, such as the head and neck, are damaged by long-term sun exposure, and the pigmented nevi on the palms of hands, feet and genitals are often rubbed, or broken for other reasons, so that the body makes mistakes in DNA when repairing itself, they may develop into melanoma. How to distinguish, whether it is a pigmented mole or a tumor? Since the disease is like a normal nevus or a small ulcer in the early stage, it is not painful or itchy, so it is not easy to attract the attention of patients and doctors. However, metastasis occurs once it grows through the deep layer of skin, usually 4mm thick, and if treatment is further delayed, distant metastasis will soon occur to the advanced stage of the disease. If the moles on your body show the following conditions, you should pay special attention to them 1.Asymmetry: One half of the pigmented mole looks asymmetrical to 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 nevus is 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 pigmentation spot is >5~6mm in diameter or the pigmentation spot grows significantly, melanoma is usually larger than normal moles, keep an eye on pigmentation spots >5mm in diameter, and it is better to do biopsy evaluation for pigmentation nevi >1cm in diameter. 5. Bulging: In some early melanomas, the entire tumor will have a slight bulge.