Anthony Visioni and Julian A. Kim

Introduction

Several cancers, including breast cancer and melanoma, are similar in that regional lymph node metastasis greatly impacts treatment, chance of recurrence, and survival rate. Therefore, management of regional lymph node metastasis is of great interest in patients with these diseases. Previously, the standard of care for a patient diagnosed with invasive cancer was to perform a lymphadenectomy—removal of all regional lymph tissue. Although associated with high morbidity, the procedure was performed to diagnose and treat regional lymph node disease and to correctly stage a patient for further systemic therapy.

Sentinel lymph node biopsy (SLNB) has dramatically changed the management of breast cancer and melanoma patients. The procedure was first described in 1977 by Cabanas for penile cancer; diagnostic and therapeutic applications have since grown. Instead of routine lymphadenectomy, patients who are clinically node negative can now be accurately staged with minimal morbidity.

Dye/Radiotracer and Injection Sites

The injection site for the blue dye or the radiotracer can be either over the tumor or the areola (Fig. 48-1). In the operating room the surgeon then looks for a blue lymph node (if dye is used), a radioactive lymph node (if radiotracer is used), or both. With a radiotracer, multiple nodes may be radioactive. It is important to search for the node with the highest level of radioactivity. This node, as well as all nodes with more than 10% of the highest count, should be removed for pathologic evaluation.

In breast cancer, the choice of blue dye or radiolabeled colloid to perform SLNB has been the subject of multiple studies. Some studies report that the combination of blue dye and radiolabeled colloid is optimal for identification of sentinel nodes, whereas other studies show equivalence. In general, the choice of blue dye or radiolabeled colloid should be dictated by surgeon preference as well as contraindications in patients (e.g., pregnancy, allergy).

Lymphatic Drainage

Another important consideration is the choice of injection site. The lymphatic drainage of the breast and overlying skin are the same: both drain to the axillary lymph nodes. Therefore, intradermal injection (vs. peritumoral injection) of radiotracer is an acceptable practice. Periareolar and subareolar injections work equally well for SLNB. However, intradermal injection of blue dye may lead to skin discoloration and should be avoided in breast cancer. This approach contrasts with melanoma, in which intradermal injections are required; the discoloration of the skin is irrelevant because a wide local excision will be performed at the time of SLNB (Fig. 48-1).

In the case of melanoma, injection of radiolabeled colloid allows for preoperative lymphoscintigraphy. The lymphatic drainage is more variable in melanoma; therefore, lymphoscintigraphy with use of intraoperative gamma probe increases the likelihood of identifying the sentinel lymph node in melanoma involving various anatomic locations.