After looking at the pathology report, physicians assign a “provisional stage" to melanomas as a means to classify their patients according to their chances of being cured, and to guide their choices of further testing and treatment. In general, doctors inte­grate information on the primary tumor with data on the presence and location of metastases to arrive at the final stage. For instance:

•  Stages I and II: The tumor is apparently confined to the site where it started up to 1.5 millimeters thick; there is no evidence of nearby skin or lymph node involvement or of distant metastasis. The five-year survival rate depends on the melanoma’s thickness (and other features) and varies from about 95 percent for people who have stage IA lesions (that are a millimeter or less in thickness, that are not ulcerated and that are level II or level III) to just under 50% for patients with stage IIC lesions (that are thicker than 4 mm and are ulcerated.) 

•  Stage II: The primary tumor is more than 1.5 millimeters thick; no evidence of spread. The five-year survival rate is about 80 percent. Note that the outcome for patients with Stage I and II disease can be more accurately forecast with the predictive models described earlier.

•  Stage III: Melanoma has spread beyond the place where it started and into the nearby skin or, more commonly, into the lymph glands (nodes) near the primary tumor. (The regional nodes for a melanoma on the right forearm, for example, are in the right armpit.) The five-year survival rate depends on the number of nodes involved and whether they have within them only microscopic amounts of tumor or enough to make the glands big enough to feel (this is called “macroscopic” involvement.)   For patients with just 1 microscopically involved node the survival rate is as high as 70%, while for those with easy to feel, enlarged nodes and more than three affected the survival rate is as low as 15%.

•  Stage IV: Colonies of melanoma cells are evident beyond the regional nodes (for example, in the distant skin or nodes or in the organs in the body). The five-year survival rate is about 10 percent. 

Source: Melanoma Prevention, Detection and Treatment, New Haven: Yale University Press. 2005 by Catherine Poole and DuPont Guerry, M.D.