Omitting Blue Dye Prior to Mohs Surgery for Melanoma: Is it Safe?

Use of blue dye injection during sentinel lymph node biopsy (SLNB) prior to Mohs surgery for malignant melanoma in the lower extremities can be safely omitted without compromising the accuracy of the biopsy, according to the results of a new study out of Asia.

“The omission of blue dye injection can avoid both skin complications and rare but dangerous anaphylactic reactions; it may also enable SLNB under local instead of general anesthesia, which is safer and reduces time and costs,” wrote researcher Ki-Hoon Song, MD, PhD, of the National Cancer Center in South Korea, and colleagues, in the British Journal of Dermatology.

According to the study, SLNB is traditionally performed using a triple technique: lymphoscintigraphy (injection of a radiolabeled tracer), blue dye injection, and a radioisotope detection using a gamma probe. However, blue dye injection may cause pathologic misinterpretation and obscure clinical margins.

Here, Song and colleagues retrospectively evaluated 72 patients from Dong-A University Hospital in South Korea, who underwent Mohs microscope surgery with or without SLNB using preoperative localization of the primary melanoma via lymphoscintigraphy and intraoperative confirmation using a gamma probe. All biopsies omitted blue dye injection.

The majority of included patients (65 of 72) underwent SLNB. The success rate of SLNB was greater than 98.5%. None of the sentinel lymph nodes successfully localized via lymphoscintigraphy were false negative.

About one-third of patients (32.8%) had at least one sentinel lymph node that was positive for metastasis. Subsequently, 85.7% of these patients underwent complete node dissection; 19% had additional metastatic nodes.

With a median follow-up of 48 months, 6.9% of patients had local recurrence after Mohs surgery, 6.9% had regional recurrence, and 12.3% of patients had distant metastases.

Presence of positive sentinel lymph nodes was significantly associated with recurrence (relative risk, 3.34; P = .004), but not with death. There was no overall survival difference for patients with positive compared with negative sentinel lymph nodes.

The 5-year overall survival rate was 78.5% and the 5-year disease-free survival rate was 75.9%, “similar to or higher than those reported from Asian countries in general or from studies of patients who underwent classic SLNB,” the researchers reported.

“Our data show that performing SLNB while omitting blue dye injection can still yield a high biopsy success rate (98.5%) that is similar to the 95%–100% detection rate achieved in previous studies that used a combination of lymphoscintigraphy and blue dye injection, and is higher than the rates reported when using blue dye injection alone (52%–95%),” the researchers wrote.

Based on these results, the researchers concluded that blue dye could be safely omitted at the surgeon’s discretion.