What's the next step if the sentinel lymph node (SLN) cannot be located after 20 minutes of using a gamma probe and blue dye during a sentinel lymph node biopsy (SLNBx) for breast cancer?

Management of Failed Sentinel Lymph Node Biopsy in Breast Cancer

If the sentinel lymph node cannot be identified after 20 minutes of searching with gamma probe and blue dye, you should proceed with a complete axillary lymph node dissection (ALND). 1

Understanding Failed SLN Identification

When sentinel lymph node biopsy (SLNB) fails despite using both radiotracer and blue dye techniques, this represents a technical failure that requires a definitive management approach to ensure proper staging and treatment of the breast cancer patient.

Reasons for Failed SLN Identification:

• Disruption of lymphatic flow from previous surgery
• Metastatic deposits blocking lymphatic drainage
• Technical issues with injection technique
• Close proximity of SLN to the injection site
• Anatomical variations in lymphatic drainage

Evidence-Based Management Algorithm

1. Confirm thorough search technique:

   • Ensure proper search pattern (raster pattern of parallel lines 2cm apart)
   • Verify scanning speed (few centimeters per second)
   • Check for proper probe angulation over potential hot spots 1

2. If SLN not identified after 20 minutes:

   • Proceed directly to complete axillary lymph node dissection 1
   • This is consistent with established guidelines that state: "If an ipsilateral SLN is not identified, complete lymphadenectomy is recommended" 1

3. Document in operative report:

   • Techniques used (gamma probe + blue dye)
   • Duration of search (20 minutes)
   • Reason for proceeding to ALND

Supporting Evidence

The recommendation to proceed with ALND is based on strong evidence from multiple guidelines. A large prospective study of 466 patients showed that failure to identify an SLN occurred in 5.6% of cases, and in all these patients, a complete axillary dissection was performed 1. This approach ensures proper staging and reduces the risk of leaving potentially metastatic nodes behind.

The combination of radiocolloid and blue dye provides the highest SLN detection rate (97.7%) compared to either technique alone 1, but even with optimal technique, identification failures occur. In these cases, ALND remains the standard approach to ensure proper staging and regional control.

Important Considerations

• Metastatic risk: Among patients who failed SLN mapping in one study, 15.4% had metastatic disease found on ALND 1, highlighting the importance of not leaving the axilla unaddressed

• Avoid repeated injections: While some might consider re-injection of tracer, evidence suggests this is unlikely to be successful after 20 minutes of searching and may delay definitive management

• Preoperative lymphoscintigraphy value: For future cases, consider that preoperative lymphoscintigraphy may help predict successful intraoperative SLN identification 2

• Documentation importance: Clearly document the failed attempt at SLNB in the operative report to justify the need for ALND

By proceeding with ALND after a failed SLNB attempt, you ensure appropriate staging and regional control for your breast cancer patient while minimizing the risk of leaving potentially metastatic nodes behind.