The investigators are doing this study to improve our ability to identify which people with many moles on their skin are most likely to develop skin melanoma. The investigators hope to identify features of moles that are associated with melanoma risk. The investigators hope to use this information to customize and tailor melanoma screening to the individual patient based on a better estimate of their individual risk.

Inclusion Criteria:

• Patients ≥ 18 years of age
• High-risk nevus phenotype (≥ 50 nevi (≥ 2mm in size) and ≥ 1 atypical nevus)
• First presented to MSKCC for cutaneous melanoma-related care on or after April 2016
• Cases: diagnoses of unequivocal invasive cutaneous melanomas (AJCC Stages I-IV) confirmed by MSKCC pathology on or after April 2016
• Cases: completion of surgical treatment of primary melanoma
• Ability to sign or verbally consent to the informed consent

Exclusion Criteria:

• Controls: Histopathologically borderline melanocytic tumors for which melanoma could not be excluded or that were treated as possible melanomas.
• Known germline high-penetrance melanoma predisposition mutation (that is, CDKN2A, CDK4, and BAP1)
• Cases: history of invasive cutaneous melanoma (AJCC Stages I-IV) not confirmed by MSKCC pathology
• History of acrolentiginous type of cutaneous melanoma or history of mucosal melanoma
• Cases and controls: prior administration of systemic medications known to modify nevus phenotype, including but not limited to: MEK inhibitors (trametinib, cobimetinib, etc.), BRAF inhibitors (vemurafenib, dabrafenib, etc.), and immunotherapy (pembrolizumab, nivolumab, atezolizumab, ipilimumab, etc.). Controls: history of Stage 0-IV melanoma confirmed by MSKCC pathology
• History of limb amputation or other condition (e.g., tattoos, burns) per investigator discretion that would modify nevus phenotype
• Physical inability to undergo total body photography or reflectance confocal microscopy imaging (that is, remain relatively still for durations of 3-5 minutes)
• Known hypersensitivity to adhesive rings used for reflectance confocal microscopy
• Inability to give informed consent
• Have skin afflicted with anther skin condition (for example, psoriasis) that would affect ability to characterize nevus phenotype (per investigator discretion)
• Familial cutaneous melanoma history (families with at least one invasive melanoma and two or more other diagnoses of invasive melanoma or pancreatic cancer among first- or second-degree relatives on the same side of the family). We will confirm melanoma family history via medical record documentation, whenever possible, as recommended by previous studies that disproved about half of the reported family histories of melanoma among first-degree relatives in case-control studies.
• Age 70 or above

All patients in the Melanoma Screening and Surveillance Program (MSSP).