Christine J. Ko, MD, is Professor of Dermatology and Pathology at Yale University. She is board certified in both dermatology and dermatopathology. She is the author of several academic texts in dermatology and dermatopathology, including Dermatology Essentials and Dermatology: Visual Recognition and Case??Reviews. Ronald J. Barr, MD, is Professor Emeritus of Dermatology and Pathology at University of California, Irvine. He??is board certified in anatomical pathology, dermatology, and dermatopathology. He is recognized for his many contributions in dermatopathology, involving both neoplastic and non-neoplastic disorders.