Preoperative contrast-enhanced ultrasound combined with intra-lymph node methylene blue injection for sentinel lymph node identification: a minimally invasive sentinel lymph node biopsy tracing approach.

[OBJECTIVES] To investigate the significance of preoperative contrast-enhanced ultrasound (CEUS) coupled with injections of methylene blue (MB) into the lymph nodes, alongside intracutaneous injections of indocyanine green (ICG) for sentinel lymph node (SLN) identification in early breast cancer.

[MATERIALS AND METHODS] All patients from a single institution were prospectively randomized into two groups: CEUS Group (preoperative SLN-CEUS coupled with injections of MB into the lymph nodes, with ICG intracutaneous injections for SLN identification during surgery) and Blue Staining Group (intracutaneous injections of both ICG and MB for SLN mapping during surgery). Pathological results served as the gold standard. Multivariate logistic regression analysis was used to identify independent risk factors for SLN metastasis. Areas under the receiver-operating characteristic curve (AUC) were used to evaluate the ability of CEUS to diagnose SLN metastasis.

[RESULTS] 134 patients were enrolled (CEUS Group: 76 patients, Blue Staining Group: 58 patients). CEUS Group achieved a 100.0% success rate in detecting SLNs, with identifying a median of 1 SLN, while Blue Staining Group identifying a median of 4 SLNs per case (p < 0.001). CEUS enhancement pattern was the only factor independently linked to SLN metastasis (p < 0.001), showing a sensitivity of 90.5% and a specificity of 94.5%. The AUC for identifying SLN metastasis was 0.925.

[CONCLUSIONS] CEUS enhancement pattern is helpful to determine the SLN metastasis. Preoperative CEUS, combined with MB injections into lymph nodes and intracutaneous ICG injections during surgery, provides a reliable method for localizing SLNs. This approach minimizes the risk of non-SLNs excisions.

[KEY POINTS] Question Despite the critical role of sentinel lymph node (SLN) detection in surgical outcomes, current preoperative imaging-guided SLN tracing remains in the exploratory stage. Findings Contrast-enhanced (CE) US achieved 100% SLN detection success with fewer non-target lymph nodes excised versus blue dye, demonstrating superior sensitivity and specificity metastatic prediction. Clinical relevance Preoperative SLN-CEUS, combined with intralymphatic methylene blue injection and intracutaneous indocyanine green administration during surgery, enables precise SLN identification and metastasis prediction. This approach minimizes the risk of unnecessary non-SLN resection during SLNB.