Identification and preservation of stained non-sentinel lymph nodes in breast cancer

Sentinel lymph nodes (SLNs) are the first lymph nodes that receive lymphatic drainage from the breast. However, all stained lymph nodes are dissected as SLNs during surgery. The present study aimed to identify and preserve the stained non-SLNs and evaluate the safety during sentinel lymph node biopsy (SLNB) in breast cancer. SLNB was performed with a methylene blue and indocyanine green double-tracer technique. The first lymph node, which was connected with lymphatic vessels from the breast, was designated as the true SLN. The lymph node that was directly connected with the output lymphatic duct of the SLN was defined as post-SLN (poSLN), whereas the stained poSLN was designated as non-SLN. Both the stained SLN and non-SLN were sent to the pathological department for definitive diagnosis. The present study demonstrated that intraoperative dissection of the lymphatic network could distinguish true SLNs and stained non-SLNs. The number of stained lymph nodes was time-dependent. Not all stained lymph nodes were real SLNs, whereas the poSLNs would be stained if the staining time interval was inappropriate. The data indicated that the poSLNs were negative for metastasis when the SLNs were negative for metastasis. Stained lymph nodes may contain non-SLNs in addition to SLNs. Resection of all stained lymph nodes is not recommended. To reduce the morbidity due to SLNB complications, the identification and preservation of stained non-SLNs during SLNB is feasible and warrants further study in the era of precision medicine.