A black bump on the waist may be caused by warts, pigmented nevi, melanoma and other diseases. 1. Warts: the etiology is mainly related to human papilloma virus infection, low immunity, trauma and other reasons may increase the chances of disease. Patients will appear locally soybean size or larger pimples, usually gray-brown, brown, etc., warts surface roughness, can see small black spots, look will lead to a black pimple on the waist. 2. pigmented nevus: it is a benign tumor occurring in the skin, most of the congenital pigmented nevus, there are also acquired due to ultraviolet radiation and other causes. Clinical manifestations are brown or black papules with uniform color and clear boundary. 3. Melanoma: generally refers to malignant tumors occurring in the skin, mainly caused by DNA damage, fair complexion, excessive exposure to ultraviolet rays can also induce the disease. Patients will have local pigmented spots, black, brown, gray, etc. The tumor has a slight bulge in the early stage, and some patients may have black bumps on the waist, which can be accompanied by uneven color and unclear border performance. There may be other reasons that lead to a black pimple on the waist, it is recommended that the patient go to the regular hospital for consultation and examination, and after clarifying the cause of the disease, symptomatic treatment.