This book provides the most comprehensive and up-to-date knowledge of lymph node micrometastasis (LMM) and sentinel node navigation surgery (SNNS) in gastrointestinal cancers. Lymph node metastasis is a critically important prognostic factor in gastrointestinal tract cancers such as tumors of the esophagus, stomach, and colorectum. An understanding of the basic aspects of lymphatics and lymph nodes, including anatomy, histology, physiology, immunology, and molecular biology, is fundamental for physicians who are involved in cancer treatment. Furthermore, owing to the development of molecular and biological methodology, the precise recognition of LMM and its clinical significance have been clarified recently. At the same time, SNNS has actually been anticipated in treatment of breast tumors, and it is now being introduced in gastrointestinal tract cancer. For the application of SNNS, the detection of lymph node metastasis including LMM is extremely significant, because the presence of LMM determines the direction for surgery and chemo and/or radiation therapy. With these considerations in mind, the expert contributors to this book review basic and clinical approaches for LMM and SNNS including methodology for gastrointestinal cancers. Thus this volume benefits not only surgeons who treat gastrointestinal cancers but also clinical oncologists and medical scientists such as physiologists and pathologists.