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Deeper dissection may reveal some blue lymphatic channels (Figure 7) flowing toward the hot region where a lymph node is palpable. The lymph node is dissected free along with any neighboring lymph nodes that are blue or significantly hot (Figure 8). The definition of “significant” is any lymph node that has a radioactivity level greater than 10 percent of the hottest sentinel node or a level greater than two or three times the background level of the axillary tissue. Following removal of the sentinel nodal tissue, the incision is explored with the gamma probe for any other lymph nodes with significant radioactivity. A basal background level (Figure 9) should be present except when the detector is pointed toward the tumor or biopsy injection site. Additionally, any firm or abnormal lymph nodes should be removed.

The nodal tissue removed is examined and the individual lymph nodes are separated. One node, the sentinel node, should be quite hot, while its neighbors are much less so (Figure 10). In the example shown, lymph node A is labeled as the principal sentinel lymph node. Lymph node B is labeled as a sentinel node. Node C is not a sentinel node, as its counts are less than 10 percent of the principle sentinel node and it is not blue.

If the sentinel lymph node is in the typical low axillary region, careful hemostasis is obtained. A decision must be made as to whether to proceed with a standard axillary node lymph dissection (ALND) through a new incision or through extension of the existing incision. If a new incision is required, then closure is performed. Scarpa's fascia and the subcuticular fat are closed with interrupted 00 absorbable sutures. The skin is approximated with 00000 absorbable sutures.

Most patients who have both SNLD and ALND are observed overnight until the effects of the general anesthesia have cleared. Oral intake is resumed as tolerated and oral pain medications are given. The serous output of the closed-suction Silastic drain is monitored. Often it is removed before the patient is discharged or whenever the output falls to less than 30 mL per 24 hours.

Patients with only an SLND are usually operated on in an ambulatory setting. They can be discharged home within a few hours when they are alert and have stable vital signs according to the discharge protocol of the surgical unit.