This book describes a standardized method for classifying and reporting invasive endometrial malignancies via direct endometrial sampling. Featuring a wealth of color illustrations, it provides specific diagnostic categories and cytomorphologic criteria to promote uniform and reliable diagnoses. It also describes the history of directly sampled endometrial cytology, reviews the sampling techniques and algorithmic approach, discusses specimen adequacy, and outlines challenges for the future.The Yokohama System for Reporting Endometrial Cytology - Definitions, Criteria and Explanatory Notes offers a valuable resource for researchers at clinical cytopathological laboratories around the world whose work involves gynecological cytology, oncology, pathology, and cytopathology. It will also appeal to researchers in the fields of cytotechnology, basic science, pathology and related industries, medical residents and clinicians.