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To find the sentinel lymph node, a radioactive tracer and often a blue dye are injected near the tumour. Severe allergic reactions to the blue dye are rare (about 2 in 1,000 in the largest pooled study) but can come late, so the team asks about allergies beforehand and watches you closely for at least an hour. Your urine may be blue for a day and the skin can stay blue-stained for a while.
NICE NG101 tells UK breast teams to perform SLNB 'using the dual technique with isotope and blue dye' (2009 recommendation, unchanged in the current guideline). In a systematic review of 24 prospective studies, adding blue dye to isotope raised the identification rate (OR 2.03) but did not lower the false-negative rate. Isosulfan blue: hypersensitivity in about 2% (label), with life-threatening anaphylaxis possible; risk is higher with asthma, allergies, drug reactions or a previous reaction to triphenylmethane dyes; monitor for at least 60 minutes with trained staff and resuscitation available; do not mix with lidocaine in the same syringe; pulse oximetry reads falsely low (maximal at 30 minutes). A 2025 meta-analysis (8 studies, 19,183 breast patients) found 11.65 adverse events per 1,000 and 1.86 per 1,000 needing vasopressors, with no deaths; intraparenchymal injection had more events than peritumoral. NAP6 (UK, 266 severe perioperative anaphylaxis cases) identified Patent Blue as the culprit in 9 of 199, with delayed onset compared with antibiotics and neuromuscular blockers. Technetium tilmanocept: ask about dextran reactions and have resuscitation ready. Indocyanine green fluorescence was equivalent to isotope and superior to dual isotope and blue dye for identification in a 2020 meta-analysis.
Why: Using two tracers finds the sentinel node more often than isotope alone.
“Perform SLNB using the dual technique with isotope and blue dye. [2009]”
NICE 2018 · Not graded (NICE NG101 1.4.10, 'perform', 2009)
Why: Allergic reactions to the dye are more likely in these people, and the team can plan for that or choose another tracer.
“Reactions are more likely to occur in patients with a history of bronchial asthma, allergies, drug reactions or previous reactions to tri-phenylmethane dyes.”
US FDA (DailyMed) 2026 · Label warning (no grade)
Why: This tracer is chemically similar to dextran, which can cause serious allergic reactions.
“Before administering Lymphoseek, ask patients about prior hypersensitivity reactions to drugs, especially to dextran and modified forms of dextran.”
US FDA (DailyMed) 2026 · Label warning (no grade)
Why: A severe allergic reaction needs treatment within minutes.
“Have resuscitation equipment and trained personnel immediately available at the time of Lymphoseek administration.”
US FDA (DailyMed) 2026 · Label warning (no grade)
Why: Mixed in one syringe, the two form a solid deposit at once.
“The admixture of isosulfan blue injection 1% (with local anesthetics (i.e. lidocaine)) in the same syringe results in an immediate precipitation of 4% to 9% drug complex. Use a separate syringe to administer a local anesthetic.”
US FDA (DailyMed) 2026 · Label warning (no grade)
Why: Unlike reactions to antibiotics, reactions to blue dye often appear well after the injection, sometimes after surgery has moved on.
“Monitor patients closely for at least 60 minutes after administration of isosulfan blue injection 1%. Trained personnel should be available to administer emergency care including resuscitation.”
US FDA (DailyMed) 2026 · Label warning (no grade)
Why: The blue colour in the blood fools the finger probe for up to a few hours.
“Isosulfan blue injection 1% interferes with measurements of oxygen saturation in peripheral blood by pulse oximetry and can cause falsely low readings. The interference effect is maximal at 30 minutes and minimal generally by 4 hours after administration.”
US FDA (DailyMed) 2026 · Label warning (no grade)
Why: Knowing in advance prevents alarm; the skin staining can last a long time.
“Inform patients that urine color may be blue for 24 hours following administration of isosulfan blue injection 1%.”
US FDA (DailyMed) 2026 · Label instruction (no grade)
How care is usually carried out, read from the guidelines and standards cited. Your own team's protocol and their judgement come first; this page is for understanding it, not for doing it yourself.
In the UK, NICE NG101 sets the dual technique (isotope plus blue dye) for breast cancer. The evidence for blue dye is a higher identification rate without a lower false-negative rate (BMC Cancer 2016), at the cost of rare severe allergic reactions (1.86 per 1,000 needing vasopressors in the 2025 meta-analysis; 9 of 199 culprit agents in NAP6). Safety readiness comes from the product labels: ask about risk factors, have resuscitation ready, observe for at least 60 minutes, and allow for late onset and false pulse oximetry readings. The EANM/SNMMI procedure guideline, which sets injection technique and imaging, could not be read.
NICE 2018 · BMC Cancer 2016 · European Journal of Breast Health 2025 · Royal College of Anaesthetists (British Journal of Anaesthesia) 2018 · US FDA (DailyMed) 2026 · US FDA (DailyMed) 2026
Where it differs: Uses a fluorescent dye seen with a near-infrared camera, alone or with isotope, avoiding blue dye's allergy risk and tattooing.
Evidence: Meta-analysis of 10 studies: ICG equivalent to isotope and superior to dual isotope and blue dye for identification; not yet the NICE standard.
Where it differs: Omits blue dye where lymphoscintigraphy shows a node, to avoid dye reactions and staining.
Evidence: Dual tracers' advantage was not significant in studies with a high proportion of positive lymphoscintigraphy (OR 1.41, not significant), and dual tracers did not lower the false-negative rate.
Where it differs: Injects isosulfan blue around the tumour rather than into the breast tissue.
Evidence: Fewer adverse events (7.04 vs 15.16 per 1,000, p=0.02) in a meta-analysis of observational studies; no dose-response with volume.
To find the first lymph node a breast cancer drains to, UK surgeons inject a radioactive tracer and a blue dye. The blue dye is one of the causes of severe allergic reactions under anaesthesia and stains the skin. Pooled studies suggest a green fluorescent dye finds the node as well as the tracer and better than the two together, and that the blue dye does not lower the rate of missed cancer.
| Recommendation | Grade, as printed | Source |
|---|---|---|
| Isosulfan blue hypersensitivity rate “Hypersensitivity Reactions: Hypersensitivity reactions occur in approximately 2% of patients and include life threatening anaphylactic reactions with respiratory distress, shock, angioedema, urticaria, pruritus.” | Case series reported in the label | US FDA (DailyMed) 2026 |
| Severe reactions to isosulfan blue are uncommon “The rate of Grade I reactions was 7.96 per 1,000 (95% CI 4.08-15.46); Grade II 0.08 per 1,000 (95% CI 0.00-1.31), Grade III 1.86 per 1,000 (95% CI 0.94-3.66), with no reported mortalities.” | Meta-analysis of 8 observational studies, 19,183 patients | European Journal of Breast Health 2025 |
| Patent Blue is a recognised cause of perioperative anaphylaxis, with delayed onset “Onset was rapid for neuromuscular blocking agents and antibiotics, but delayed with chlorhexidine and Patent Blue dye.” | National audit, 266 reports (NAP6) | Royal College of Anaesthetists (British Journal of Anaesthesia) 2018 |
| Adding blue dye raises identification but not the false-negative rate “Dual tracers did not significantly lower the false-negative rate compared with radioisotope alone (OR = 0.76, 95% CI 0.44-1.29, P > 0.05).” | Systematic review of 24 prospective studies | BMC Cancer 2016 |
| Management of perioperative anaphylaxis could be better “Management of perioperative anaphylaxis could be improved, especially with respect to administration of epinephrine, cardiac compressions, and i.v. fluid.” | National audit (NAP6) | Royal College of Anaesthetists (British Journal of Anaesthesia) 2018 |
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