SNL and DCIS surgery

A sentinel node is nothing more than the first in a chain of nodes. So being first in line, it's the one most likely to contain cancer if there is any in the nodes and it's often the only one positive.  As far as I know, there are three ways to locate a sentinel node. One is using just a radioactive tracer, a second way is using just a blue dye and the third is using both the dye and the radioactive tracer. Regardless of which method is used, it's all just about locating the sentinel node(s) so that it can be removed and examined. They  won't necessarily know whether or not the node is cancerous until the pathologist examines it although sometimes it's blatantly obvious to the surgeon just by looking at it.