The sentinel lymph node concept is meeting with steadily growing interest and is being extended to the different sites of the primaries. In addition, the concept is being applied in an increasingly sophisticated manner. In this book the practical application of the sentinel node concept is evaluated from the points of view of pathology, radiodiagnosis and nuclear medicine diagnostics, surgical treatment and clinical oncology. The concept is analyzed for breast cancer, malignant melanoma, tumors of the face, oropharynx, lung, gastrointestinal and urogenital tract. The first part of the book describes the function and use of the nuclear medicine equipment, the tracers used, colloid solutions and modern developments in histological and immunohistochemical lymph node investigations, as well as possible pitfalls. The consequences of false-negative results are clearly delineated. In the second part, specific tumor-related problems are described.