What is a "sentinel lymph node" and how is it related to skin cancer?

What is a "sentinel lymph node" and how is it related to skin cancer?

In malignant melanoma, when those cells do spread to other organs, usually the first organ that they do so is to the lymphatic system, and that would include a lymph node. The first lymph node that the malignant melanoma goes to is called the sentinel lymph node, as in a sentry, or the lymph node that is first approached before other lymph nodes are addressed. If one finds that the sentinel lymph node has no involvement with the malignant melanoma, the inference is that the other lymph nodes would not as well. So, the sentinel lymph node is often removed and looked at microscopically to see whether or not there is any micrometastases in that lymph node. Absence of micrometastases is felt to be a very good prognostic sign for the melanoma that the lymph node was draining.