The etiology of malignant melanoma is not fully understood, but is generally considered to be related to the following factors 1. Racial inheritance: the incidence is higher in Caucasians than in Yellow and Black people. Some malignant blacks have a family history of inheritance in an autosomal dominant manner. 2, sunlight: is an important factor in the occurrence of the disease. 3, trauma and stimulation: trauma and stimulation can make benign pigmented skin disease malignant.