NEW YORK (Reuters Health) – Methylene blue has certain advantages over isosulfan blue in sentinel lymph node procedures, but the risk of a palpable mass at the injection site is increased with methylene blue, according to the findings of a retrospective study.

Isosulfan blue was the first dye used for sentinel node identification, but it is expensive and can cause allergic reactions. On the other hand, methylene blue is cheap but is associated with skin complications, Dr. Ian K. Komenaka and colleagues at the Maricopa Medical Center, Phoenix, Arizona, note in their report in the February issue of the Archives of Surgery.

They therefore conducted a retrospective records review of all sentinel node procedures at their institution to evaluate differences in outcomes and complications using methylene blue or isosulfan blue.

The study included 84 patients investigated with isosulfan blue and 110 with methylene blue.

The two dyes were equivalent in performance. The sentinel node identification rate was 100.0% in the isosulfan blue group and 99.1% in the methylene blue group (p>0.99), while more sentinel nodes were identified using methylene blue versus isosulfan blue (mean, 2.7 vs 2.1; p=0.03).

Isosulfan blue interfered with pulse oximetry readings, but this was not the case with methylene blue, according to the report. Infections and hematomas were rare in both groups, and there were no allergic reactions.

“However, in 9 of 110 patients (8.2%) in the methylene blue group, a local inflammatory reaction occurred that resulted in no superficial skin changes but caused a palpable mass at the site of injection. No injection site reactions were noted in the isosulfan blue group,” the investigators report.

One patient had the mass excised, and biopsy showed fat necrosis and fibrosis. All but one of the other masses resolved within a year.

The current cost of isosulfan blue for sentinel node mapping is $479 compared with $6 for methylene blue, Dr. Komenaka and colleagues point out. “However,” they add, “the anxiety related to a persistent injection site mass and the workup cost of a new breast mass must also be factored into the expense.”

Still, they conclude that methylene blue is a satisfactory replacement for isosulfan blue. “Because of the significant economic advantage, the absence of anaphylactic reactions, and the lack of interference with pulse oximetry, methylene blue has become the product of choice at our county institution.”

Arch Surg 2011;146:137-141.