The sudden appearance of black patches on the stomach may be caused by localized melanosis, skin bruising, melanoma, etc. General treatment, physical therapy, surgery, etc. are needed. 1. Localized melanosis: it may be caused by genetic factors, sunlight exposure, inflammation, etc. If it does not affect the appearance, it usually does not need special treatment, but should avoid ultraviolet radiation. If it affects the appearance, laser treatment can be taken. 2. Skin bruise: it may be caused by the impact of the skin on the stomach, most of them are not serious, and can be observed and treated, and generally can subside by themselves. 3. Melanoma: it is a kind of malignant tumor of skin, the development tends to be more rapid, once diagnosed, it should be timely to take surgical treatment, do extensive resection, for the expansion of the treatment 4~6 weeks after the operation generally need to do lymph node dissection. Sudden appearance of black patches on the stomach may also be other causes (such as acanthosis nigricans), if accompanied by uncomfortable symptoms, should be timely to the hospital.