After cancer is diagnosed, the next step is for doctors to determine how extensive the cancer is, through a process called staging. Staging is important because the treatment and prognosis (how well the patient is likely to fare) differ greatly for different stages of cancer. You don't hear much about staging for most skin cancers other than melanoma because most of these cancers are diagnosed while they are still confined to a small area, and therefore formal staging is not needed. However, staging is an important part of the process of diagnosing and treating melanoma and many other types of cancer.
The staging of melanoma involves determining how thick the tumor is, how deeply it has penetrated into the skin, whether cancer cells have spread to nearby lymph nodes, and whether cancer cells have spread to other parts of the body.
Melanoma is staged using the numbers 0 through IV, where 0 is the least advanced cancer and IV is the most advanced.
Stage 0 melanoma is a cancer that is limited to the epidermis (the upper layer of the skin) and has not spread. This type of melanoma is also called in situ melanoma. (In situ means confined to its original location and is good news when it comes to cancer.) Melanomas at this stage have a very high cure rate. Treatment consists of surgery to completely remove the melanoma.
Stages I and II melanoma are also confined to the skin, without any spread of the cancer to lymph nodes or distant parts of the body. The difference between these two stages is that stage II melanomas are thicker than stage I. Treatment for stage I and stage II melanoma, like that for stage 0 melanoma, is surgical, but a larger area of tissue surrounding the melanoma will be removed, and skin grafting may be necessary because the wound will be relatively large. In some instances, nearby lymph nodes may also be removed.
In Stage III, the melanoma has spread to nearby lymph nodes or other nearby areas. In stage III cancer, all of the affected tissues, including the lymph nodes to which the cancer has spread, and some surrounding normal tissues must be removed surgically. The prognosis for patients with stage III melanoma is not as good as that for patients with melanomas that have not spread.
Stage IV melanoma is cancer that has spread to distant parts of the body. Generally, cancer that is this advanced cannot be cured. Instead, patients receive palliative care, that is, treatment that helps to control pain and other symptoms, rather than attempting to prolong the patient's life. Surgery may be part of the treatment in some cases, but it is not expected to cure the disease. Radiation therapy, chemotherapy, and/or biological therapy may be used to relieve pain and other symptoms.