For more information regarding Bristol-Myers Squibb Clinical Trial participation, please visit www.BMSStudyConnect.com Inclusion Criteria: For Cohort 1 and 2: (Recruitment ended by 02/20/2020) - Advanced melanoma (Stage III/Stage IV) - Histologically confirmed diagnosis - Treatment decision for nivolumab monotherapy or nivolumab/ipilimumab combination therapy has already been taken For Cohort 3: (Recruitment ended by 08/31/2020) - Primary diagnosis of advanced melanoma after complete surgical tumor resection and no evidence of disease - Treatment decision for adjuvant nivolumab therapy has already been taken Exclusion Criteria: For Cohort 1 and 2: (Recruitment ended by 02/20/2020) - Current primary diagnosis of a cancer other than advanced melanoma, that requires systemic or other treatment or has not been treated curatively (as per discretion of the investigator) - Previous treatment with nivolumab, for nivolumab monotherapy cohort only - Current active participation in an interventional clinical trial For Cohort 3: (Recruitment ended by 08/31/2020) - Current diagnosis of persisting advanced melanoma or a cancer other than advanced melanoma that requires systemic or other treatment or has not been treated curatively (as per discretion of the investigator) - Current active participation in an interventional clinical trial Other protocol-defined inclusion/exclusion criteria apply