Two types of agents have been principally tested for lymphatic mapping and sentinel node identification procedures: vital blue dyes (1% isosulfan blue or methylene blue) and 99m-technetium-labeled sulfur colloid (TSC; unfiltered or filtered). Methylene blue can be used in lieu of isosulfan blue. Different injection sites of these agents may be used: peritumoral or around biopsy cavity, periareolar/subareolar, or in combination. The first method instills 3-5 mL of isosulfan blue subareolar or at 3, 6, 9, and 12 o’clock surrounding the lesion. The breast is massaged, and the axilla is incised 3-7 min later, inferior to the hair-bearing area a few cms inferior to the axillary skin fold, depending on the distance of the tumor to the axilla. Typically, blue afferent lymphatics and blue nodes are identified below the clavipectoral fascia. The surgeon should inform the anesthesiologist when injecting the dye because a transient drop in the pulse oximeter reading of 2-5% is frequently seen, with maximal drop occurring within 20-25 min after injection. This is artifactual due to effects of blue dye spectral absorption, and blood oxygen remains normal. Patients’ skin may retain a bluish hue, and the urine, stool, or emesis can be blue for up to 24 h (the patient needs to be advised of this prior to discharge). Allergic reactions consisting of “blue hives” to full-blown, life-threatening anaphylaxis have been reported following the injection of isosulfan blue dye. Methylene blue has a lower incidence of allergic reactions, but can cause skin necrosis if injected undiluted intradermally.

Sentinel lymph nodes can also be identified using TSC (˜1-2 mCi). This agent is usually injected in the nuclear medicine department the day of or the day before the operative procedure. The tracer has very low radioactivity, and no special protection is required around the patient or in handling tissue specimens. Postinjection lymphoscintigraphy is considered optional. After induction of GA or regional anesthesia, the operative field (chest and lymph node-bearing areas) is surveyed with a hand-held gamma probe (a slim rod, similar to a Geiger counter). The “hot” spot(s), denoting accumulated tracer in lymph nodes, are identified, and an incision is made in the overlying skin. It was previously customary to have a pathologist examine the sentinel node intraop using touch-prep cytology or frozen section to identify node-positive cases for proceeding with standard axillary dissection during the course of the same operation. More recent studies suggest that patients with clinically negative but 1-2 histologically positive sentinel lymph nodes do not have worse outcome if axillary lymph node dissection is omitted.

Combination of blue dye and TSC yields the highest sentinel node identification rates. Whenever the sentinel node cannot be identified, a conventional axillary dissection should be performed. Failure to identify sentinel node either by palpation or above-described techniques mandates proceeding with a standard level I and II axillary lymph node dissection. Limiting axillary lymph node dissections is now valid for patients with two or fewer positive sentinel nodes, provided the patient will be treated with postoperative whole breast or regional radiation therapy. Completion axillary dissection is performed in mastectomy-treated patients with positive sentinel lymph nodes.

Usual preop diagnosis: Invasive breast cancer