This book is structured in three major parts and the first part is a comprehensive overview of IBD-related intestinal cancer. The second and third parts provide rare and important cases on ulcerative colitis (UD) and Crohn’s disease (CD) presenting the macroscopic image of the resected specimen and analyzing the endoscopic and the pathological image to explain how to find the IBD cancer. It also delivers a detailed analysis of the histological structure of cancers. This book tries to clarify the critical but yet to be answered questions such as “Why is it so difficult to find out?”, “Why so flat?” and “How to name superficial lesion with invisible margin?” and so on.