Sentinel node biopsy is a procedure in which a small tissue sample is taken to test if the cancer has spread into the lymphatic system or lymph nodes. Lymph nodes are oval-shaped small organs, considered to be a part of the immune system, and present in various parts of the body. They are usually present near the internal organs like lungs, intestines, and stomach, and in areas like neck, armpits, and groin. Sentinel node biopsy is performed to detect melanoma and breast cancer. Sentinel nodes are the primary lymph nodes in which the drainage of the tumor is commonly observed. Usually, a tracer material is injected during the surgery, which helps the surgeon to locate the sentinel lymph nodes clearly. After the sentinel lymph nodes are removed from the body, they are further sent to the lab for detailed analysis. If the sentinel lymph nodes do not contain cancer cells, then the removal of additional lymph nodes is not required. However, if the cancer is present in the sentinel lymph nodes, then the additional lymph nodes are required to be removed for the doctor to examine the cancer spread.