Scott JF, et al. - In a population-based cancer registry, experts characterized stage IV melanoma of unknown primary (MUP). They found an increasing incidence of stage IV MUP particularly for patients less than 30 years of age. For stage IV MUP, age greater than 50 and a lack of surgical treatment were negative prognostic factors. For stage IV MUP vs melanoma of known primary (MKP), relative survival, but not 5-year adjusted disease-specific survival (DSS), was higher.