The primary objective of this study is to identify the molecular identity profiles of all cellular states that characterize the progression from benign nevi to malignant melanoma in CAYA patients with L/GCMN. The secondary objectives are: * To longitudinally characterize the cell-free DNA (cfDNA) from CAYA patients. * To improve the early diagnosis and treatments for intermediate conditions such as L/GCMN through evidence-based interpretation of personal risk from endogenous or exogenous sources. * To test pre-clinical strategies to best model and improve patient response.