Background: Sentinel node biopsy is routinely performed in patients with intermediate thickness melanoma to identify patients who may benefit from a complete lymph node dissection or immunotherapy. Three methods are used to help identify the sentinel node; lymphoscintigraphy, gamma probe and blue dye. Different dyes are available and evidence suggests that methylene blue has a lower risk of anaphylaxis than patent blue dye. However, anecdotally we have noticed inferior results with the sensitivity of methylene blue.
Method: Retrospective audit of the use of methylene blue and patent blue dye for sentinel node biopsy in melanoma patients from Waikato Hospital over a 2 year period
Results: 123 patients underwent wide local excision and sentinel node biopsy over a 2 year period (July 2020-2022). 89 patients were included in the study. Patent blue (PB) was used in 32 patients and methylene blue (MB) was used in 57 patients. A blue node was identified in 81% of PB patients and 46% of MB. A hot and blue node was identified in 78% of PB and 42% of MB patients. Literature review reports that the anaphylaxis risk is lower with methylene blue but the overall risk of anaphylaxis for sentinel node biopsy in melanoma patients is low 0.0043%. In our study there were no adverse reactions to dye but the numbers were too small for this to be significant.
Conclusion: Patent blue is more sensitive than methylene blue at helping to identify a blue lymph node.