What is the definition or description of: sentinel lymph node?

Seninel lymph node: Is the hypothetical first lymph node or group of nodes draining a cancer. The lymph node/s will be the target organs primarily reached by metastasizing cancer cells from the tumor.

A surgical procedure: This is a surgical procedure to identify the first node that receives drainage from the site of the cancer, and is thus the node most likely to have cancer if cancer has spread. It is done routinely for breast cancer and melanoma but can also be used for others. The node is removed and examined under the microscope for cancer. The results will help determine what additional treatments may be neede.