1.   If a sentinel node is cancerous, however, more nodes must be removed.

2.   If the sentinel nodes are free of cancer, the disease has not spread to the rest and no more nodes are removed.

3.   The tracer usually goes to a single node -- the sentinel node, or primary -- in the basin.

4.   Doctors then remove only these so-called sentinel nodes and see if they are cancerous.

5.   If there were a sentinel node, it absorbed the radioactive liquid and could be identified easily on scans.

6.   In cases where the sentinel node showed cancer, the rest of the nodes in the armpit were cut out.

7.   That node, called the sentinel node, emits a radioactive signal to a Geiger counter-like probe.

8.   Using the radioactive signal as a guide, the surgeon then excises the sentinel node, which is examined in the laboratory.

9.   Veronesi and his colleagues concluded that the technique could identify the sentinel node in many women with breast cancer.