Frozen sections are performed while a patient is undergoing surgery as a basis for making an immediate diagnosis that will impact treatment decisions. Frozen section diagnosis is often a highly demanding situation for the pathologist who must render a diagnosis quickly for the patient and surgeon.The Frozen Section Library Series will provide concise, user-friendly, site specific handbooks that are well-illustrated and highlight the pitfalls, artifacts, and differential diagnosis issues that arise in the hurried frozen section scenario. Nicole C. Panarelli, MD is affiliated with Weill Medical College of Cornell University, New York, NY and New York Presbyterian Hospital, New York, NY. Rhonda K. Yantiss, MD is Associate Professor of Pathology and Laboratory Medicine at Weill Medical College of Cornell University, New York, NY.