This book is a compilation of high-yield, at-a-glance summaries for various topics on which pathologists frequently need information in a quick reference format while at the microscope (or when cramming for the boards). The authors are early-career pathologists who have compiled this book from the perspective of pathologists-in-training. The focus is not organ-based histologic criteria, but rather everything else that goes into pathologic diagnoses but is difficult to keep committed to memory. The emphasis is on immunohistochemistry, special stains, grading systems, molecular markers, tumor syndromes, and helpful clinical references. The book has a unique format in that the information is presented primarily in tables and diagrams accompanied by minimal explanatory text. It is intended to serve as a ‘peripheral brain’ for pathology residents and also practicing pathologists, where frequently needed information is readily accessible and easy to navigate.