This text and the terminology developed by the Papanicolaou Society of Cytopathology (P.S.C.) represent an important advance in the field of pancreaticobiliary cytopathology. This textbook/atlas is designed to present a comprehensive and state-of-the-art approach to the cytologic diagnosis and reporting of pancreaticobiliary lesions. Chapters address each of the diagnostic categories defined by the P.S.C. The definition of each category, along with the clinical pathologic entities contained within the category, are discussed along with specific cytologic criteria for inclusion of a cytologic specimen within the category. Each chapter is lavishly illustrated, demonstrating diagnostic criteria and examples of lesions contained within the category. Additionally, appropriate ancillary testing is discussed and, where appropriate, illustrated. Each chapter concludes with a discussion of appropriateness.