Meeting Surgical Necessities for Sentinel Lymph Node Biopsy in Breast Cancer: Experience with Methylene Blue in a Colombian Hospital

To the Editor: Sentinel lymph node biopsy (SLNB) was originally developed with isosulfan blue (IB), but in most regions it is scarce and expensive, therefore substitute dyes were studied (1,2). With a growing need to offer SLNB and faced with limited resources, in 1998, we decided to use methylene blue (MB) as a substitute dye. An ethics board–approved retrospective chart review was performed on breast cancer patients who underwent SLNB from January 1998 to January 2008 at Hospital Universitario San Ignacio, a universityaffiliated, private hospital in Bogota, Colombia. According to standard criteria, in 1998, the technique was validated with an identification rate (IR) of 100% and false negative rate (FNR) of 3.3%. At that time, 5–10 mL of MB (3%) was injected peri-tumor. Between 1998 and 2004, SLNB was exclusively colorimetric. In 2004, MB was reduced to a 1.0% concentration and a volume of 1.0 mL. Radioactive, unfiltered Technetium99-labeled colloid was incorporated after acquiring a handheld gamma-probe machine. Technetium99 was administered before surgery and subsequently lymphoscintigraphy was performed. Currently, MB is administered in the sub-areola sub-dermis, followed by a 5-minute breast massage. The gamma-probe localizes the area with the highest count where the axillary incision is made. A gamma-count is done in every SLN identified and excised; the background count is accepted to be <10% of the highest count. SLNs are submitted for permanent section analysis. Information was gathered on 76 patients. Clinicalpathological characteristics of the study population are shown in Table 1. Colorimetric-based SLNB was performed in 19 patients (1998–2004), of which one did not map. Our overall IR was 98.7%. Mean number of SLNs identified was two (range: 1–7) and fifteen of 76 (19.76%) SLNs harbored metastasis. Anaphylaxis was not documented. Immediate reactions included the following: green urine and bluebreast tattooing in two different patients, both resolved within 48 hours. In addition, one patient developed focal erythema and palpable induration at the injection site several days after surgery, resolving several weeks later. In the late 1990s, a shortage of IB led to study MB as an alternative dye (1). At that time, IB was not available in Colombia and if so, the costs would have limited the number of patients who would have received it. Our global IR (including validation period) was 99%, comparable to that from other studies, which reported IRs of 99% (combined technique) and 83–93% (dye-alone mapping) (3). At around the same time in which we started validating SLNB, other Latin-American groups did the same. The detection rates reported by these groups ranged 77.8%–98% (4–7) (Table 2). Once injected, MB causes toxicity due to the formation of aldehydes and a reduction in oxidation prod-