There have been many advances in the diagnosis and treatment of cancer, but it is still a feared disease with a lot of work left to be done. The importance of gastrointestinal cancer as a frequently occurring disease goes without saying. It s for half of human cancer cases but differs from other forms of cancer. Complete prevention is possible through proper treatment of precancerous lesions. There is still no comprehensive book about prevention, early diagnosis, and proper treatment of precancerous lesions and new developed diagnostic modality, and treatment such as endoscopic treatment and minimal invasive surgery and chemotherapy and immunotherapy. Also, this book will contain conservative treatment methods for patients suffering from diverse complications. There will be plentiful clinical cases including endoscopic findings, radiologic images, pathology and treatment outcome in this book. For these reasons, this book will give very valuable information to many gastroenterologists, oncologists , surgeons and general physicians.