As a highly malignant skin tumor, early detection and early treatment of malignant melanoma is undoubtedly of great significance. For doctors and the public, the warning signs of malignant melanoma: the ABCDEs principle can help you remember those changes that should raise alarm. A – Asymmetry: One half of the pigmented nevus behaves differently from the other half. B – Border: The edges are unclear or irregular, in the form of small jagged teeth. C – Color: The color of different areas of the pigmented nevus is diverse, ranging from yellowish brown, brown or black, sometimes even white, red or blue. D – Diameter: Half of the diagnosed nevi have a diameter greater than 6 mm, but malignant nevi smaller than this diameter are not uncommon. E – Evolving, progressive change: Over time, pigmented nevi or skin lesions change in size, shape and color.