Prominent moles may become cancerous. A mole is usually located in the superficial part of the dermis, its substance is nevus cells, its interstitium is lymphatic vessels, blood vessels and connective tissue, it is round in shape and black, yellow or brown in color. They can become malignant in some cases, and frequent friction and irritation can cause them to become cancerous. Moles occur most often in children or adolescents, and may appear as pimples, warts or nodules, etc. If a prominent mole suddenly ulcerates and turns black, grows or appears as a satellite foci, it is necessary to go to the hospital for examination in time, which may be a precursor of cancer. If the boundary of the mole is not clear, the color is different shades, and it develops rapidly and forms an irregularly shaped scar, it is very likely that the pigmented mole has been transformed into malignant melanoma, and it should be diagnosed and treated in the hospital quickly, and surgical excision is required for cancerous transformation.