Melanoma stage IV is stage 4, where IV is the Roman numeral for 4. Stage IV melanoma means that the melanoma is no longer confined to the site of origin and has metastasized to distant organs. Melanoma commonly originates in the skin and mucous membranes, with the most common sites of metastasis being the lymph nodes and lungs. Once melanoma reaches stage 4, the opportunity for curative surgery is lost. Treatment primarily involves immunotherapy, targeted molecular therapy, etc., and is incurable.