http://www.cancer.gov/cancertopics/factsheet/Therapy/sentinel-node-biopsy
National Cancer Institute, National Institutes of Health
The sentinel lymph node (SLN) is the first lymph node to which cancer is likely to spread from the primary tumor. This document provides answers to questions about SLN, including what a lymph node is, what SLN biopsy is, what the possible benefits of SLN biopsy are, what the side effects and disadvantages of SLN biopsy are, and more.