A clinically useful SLN technique requires a high technical success rate, a clear definition of SLN, an algorithm taking into account that metastatic nodes not always accumulate tracer and a reproducible surgical algorithm. A definition of SLN requires knowledge on lymphatic anatomy. Unfortunately all tracers, dyes/radiotracers often result in an abundance of colored/ signaling nodes. Therefore, a definition of a SLN requires identification of efferent/afferent lymph vessels.