A sentinel lymph node is defined as the first lymph node to which cancer cells are most likely to spread from a primary tumor. Sometimes, there can be more than one sentinel lymph node.

Which node is the sentinel node?

Sentinel nodes are simply the first nodes draining a cancerous region. For breast cancer, they are usually located in the armpit. That's why healthcare providers test the sentinel nodes to see if cancer has spread beyond the original tumor.

What are sentinel nodes in the breast?

The sentinel lymph node (SLN) is the underarm (axillary) lymph node closest to a breast cancer. During surgery to remove early-stage breast cancer, the sentinel node often is removed and sent to a pathologist who determines if there is cancer in it.