Plate 202

Breast cancer patients undergoing a mastectomy or breast-conserving procedure are candidates for axillary sentinel lymph node dissection (SNLD) if there is no palpable or clinical evidence of axillary lymph node involvement. The finding of breast cancer metastases in axillary lymph nodes changes the staging of the disease, predicts the rate of recurrence and survival, and results in adjuvant treatment with chemotherapy, hormone therapy, or radiation therapy. The standard axillary lymph node dissection of level I and II nodes has significant morbidity, of which lifelong lymphedema is the most feared by patients. Using a combination of radionuclide and dye injections, the correlation of SLND and standard axillary lymph node dissection (ALND) in finding positive lymph nodes is quite high (95 percent) in the hands of an experienced surgeon. However, sentinel lymph nodes are often only identified in 90 to 95 percent of the dissections. Additionally, a false-negative finding occurs in 3 to 10 percent of the patients having SLND—that is to say, the sentinel nodes are negative, but higher nodes are found to be positive. The advantages of SLND are the fewer complications versus ALND and the ability to identify sentinel lymph nodes that are not in the traditional level I or II areas. The identification of sentinel lymph nodes focuses the histiopathologic examination, which may include immunohistochemical staining as well as the traditional hematoxylin and eosin (H&E). The importance of a micrometastases (<2 mm) is under study; however, the total number of nodes involved with metastases may influence the adjuvant therapy that is offered. Contraindications to SLND include locally advanced primary cancers (>5-cm size); suspicious, palpable axillary lymphadenopathy; multicentric primary breast cancers; prior axillary surgery; and regional breast operations (e.g., breast reduction) that alter normal lymphatic flow.

The skin should be free of infection, as should the preceding breast biopsy site. The preparation, delivery, and monitoring of the radionuclide solution for injection must be coordinated with the nuclear medicine staff.

General anesthesia with endotracheal intubation is preferred, as many patients will also have ALND and may be having a concurrent reoperation upon the breast. Most surgeons prefer that the anesthesiologist use a short-acting muscle paralyzing agent for placement of the endotracheal tube such that the motor nerves can still be identified with mechanical stimulation during the ALND.

The patient is placed in a comfortable supine position with the arm out at 90 degrees on a padded arm board (Figure 1). This position allows easy access of the breast and the axilla.

Approximately 90 minutes before the start of the operation, the surgeon injects the radionuclide solution into the breast, using sterile technique. A commercially available sulfur colloid solution using a technetium-99m tag is sterilized after passage through a 0.22-μ m filter. Four 3-mL syringes are each loaded with 1 mL of solution containing about 100 μC of radioactivity, for a total dose of about 400 μC. Shielding is not required, but the site is monitored with a radiation survey meter. The breast is prepared with an antiseptic solution and sterile paper drapes are applied. The four injection sites are anesthetized with an intradermal injection of local anesthetic. The pattern shown (Figure 2A) allows infiltration above, below, and at either end of the incision from a preceding biopsy. A long 1½-in. 25-gauge needle is used for this injection about the biopsy site or the breast cancer. Many techniques are used for injection of the radionuclide and the blue dye. The injections may be placed (1) deeply about the tumor or biopsy cavity (Figure 2), (2) superficially in the subdermal or intradermal site over the tumor or about the biopsy site scar, and (3) superficially about the perimeter of the nipple in a subareolar manner. Care must be taken not to inject into a biopsy cavity. The breast is washed and the disposal items are surveyed and disposed of in a radiologically safe manner. The patient proceeds to the operating room. After induction of anesthesia, the breast, chest, and upper arm are prepared and draped in the usual manner.

The same three techniques are available for injection of about 3 to 5 mL of 1% isosulfan blue vital dye (Figure 3). After injection, the area is massaged for a few minutes. The dermal lymphatics may then manifest a faint blue blush streaming toward the axilla. Using a hand-held gamma detector with a sterile cover, the surgeon scans toward the axilla (Figure 4) looking for the area with the highest count rate. This may be difficult to find if the breast tumor or biopsy site is high in the upper/outer quadrant, as a regional “shine through” of the injection site radioactivity may create a very high background level. The angled head of the gamma counter can be used to advantage, as it allows more medial placement of the detector with an angled view that is away from the injection site but yet still points into the axilla. If the hottest spot is near the base of the hair-bearing axilla, a transverse incision is made directly over it (Figure 5) in such a manner that the incision can be extended later in a medial manner for a standard ALND. Sharp dissection with a scalpel or electrocautery is made through the first 1 to 2 cm of fat. The probe explores the open incision to find the hottest area (Figure 6).

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