Axillary lymphatic mapping for sentinel node (SN) biopsy is the standard procedure for the surgical staging of patients with early-stage breast cancer. Sentinel lymph node (SLN) biopsy has been shown to be safe, accurate, and limits the need for traditional axillary dissection in most patients (1). Conventionally, SLN lymphatic mapping for breast cancer has involved the use of colloid radiotracer labelled with technetium 99 (2), visible blue dye (methylene blue or isosulfan blue) (3), or a combination of both (4). Best mapping results are achieved with periareolar, subdermal injection of the tracer (5,6). SLNs are defined as axillary lymph nodes in which there is the accumulation of one or more of these tracers or dyes above defined thresholds (7). Studies have demonstrated that there is surgeon-associated variation in both the number of SLNs removed and in the likelihood of finding a positive SLN (8). In large studies involving experienced surgeons, the SN detection rate using dual mapping with Tc and a visible dye is approximately 99%, therefore, use of both methods combined is recommended by some to achieve the highest accuracy of SLN biopsy and to reduce the false-negative rate (1,9).

Both traditional mapping techniques also have drawbacks that may limit their routine use (10). ^99mTc-labeled radiotracer injection requires nuclear medicine licensing, radioactive material handling regulations, and patient inconvenience with painful periareolar injections typically occurring before surgery. Although there are reports of surgeons performing Tc injections in the operating suite, this still requires regulatory resources and is not common (11). Blue dye injections can be performed during surgery, but risk skin necrosis with methylene blue injection, inhibiting its use for nipple-sparing mastectomies, and there is a risk of anaphylaxis with isosulfan blue dye injection (12,13).

Alternative techniques including indocyanine green (ICG) dye, and superparamagnetic iron oxide (SPIO) have been utilized for SLN mapping in an effort to overcome some of the limitations of traditional methods.