What distinguishes a "sentinel" node from other lymph nodes?

A "sentinel" node is significant because it is the first lymph node encountered in the lymphatic drainage pathway from a primary tumor. Its distinguishing characteristic lies in its role as the node that is the first to receive lymphatic drainage from a tumor, especially in the context of cancer metastasis. When cancer cells spread from a primary tumor, they usually travel through the lymphatic system, and the sentinel node is where this spread is first detected.

Identification of sentinel nodes is crucial in cancer staging and treatment planning since assessing whether cancer has spread to these nodes can have a significant impact on the management of the disease. If the sentinel node is free of cancer, it is often indicative that the cancer has not spread further, allowing for less invasive treatment options. Thus, option B accurately captures the primary function of sentinel nodes in the context of cancer biology and staging.