This atlas was written for general pathologists, dermatopathologists, and pathologists in training with an interest in practical diagnostic issues in the pathology of melanocytic tumors. The focus of this fascicle is on microscopic clues for diagnosis, in particular for the distinction of melanocytic nevi from melanoma. The authors also discuss the role of ancillary methods and their potential value as well as limitations in test sensitivity and specificity. This volume will help pathologists provide the most accurate diagnoses in service of their clinical care teams and their patients.