Immunohistochemistry and ancillary studies play a crucial role in diagnostic pathology. Yet, few books cover their practicality in diagnostic dermatopathology. This book provides a practical guide to the application of rapid and cost-effective immunohistochemistry, as well as ancillary studies including immunofluorescence and molecular studies. With a focus on practicality and bridging knowledge gaps, the book covers helpful diagnostic stains and pertinent ancillary studies, organized by lines of differentiation. Each chapter includes a synopsis of antibodies, immunohistochemical panels, summary tables outlining staining patterns, and case studies. Now in its second edition, this book covers entities based on lineage, including epithelial, adnexal, melanocytic, lymphoid, and soft tissue, and discusses the role of molecular studies in the diagnosis of cutaneous neoplasms and soft tissue lesions. This comprehensive volume is an essential resource for pathologists, dermatopathologists, and residents in pathology and dermatology.