Once a melanoma has been diagnosed, a process called staging provides important information about the extent of the skin cancer and its anticipated response to treatment. Your physician will assign a stage according to the degree of severity of the cancer. Melanoma staging is also useful for estimating prognosis. Generally, lower stage cancers have a better outlook for cure or long-term survival, but other factors may also affect prognosis. The stages of melanoma run from stage 0, the earliest possible stage, in which the melanoma is confined to the top layers of the skin – also known as melanoma in situ – to stage 4 melanoma, in which the cancer has spread beyond the original area of the skin and nearby lymph nodes to other organs, distant areas of the skin or distant lymph nodes.