Pathologic examination of the sentinel lymph node: what is the best method?

Area of Science:

• Oncology
• Pathology
• Surgical Oncology

Background:

• Sentinel lymph node biopsy (SLNB) is a standard procedure for staging breast cancer axillary lymph node involvement.
• The optimal pathological examination of sentinel lymph nodes (SLNs) remains a subject of debate.
• Historically, micrometastases were considered clinically insignificant, but recent studies indicate they significantly affect prognosis.

Purpose of the Study:

• To review the current evidence on the clinical significance of micrometastases in SLNs.
• To evaluate the effectiveness of different pathological examination techniques for SLNs.
• To propose an optimized protocol for the pathological examination of SLNs.

Main Methods:

• Review of existing literature and prospective studies on SLN examination in breast cancer.
• Analysis of the impact of micrometastasis size on patient prognosis.
• Evaluation of immunohistochemistry (IHC) and molecular techniques (PCR) for detecting occult metastases.
• Assessment of intraoperative examination methods (cytology, frozen section) and their limitations.

Main Results:

• Metastases as small as 2 mm are associated with a poorer prognosis, challenging the notion that micrometastases are insignificant.
• Immunohistochemistry (IHC) detects occult metastases in approximately 18% of cases that appear negative on routine stains, often indicating a worse prognosis.
• Intraoperative techniques lack sensitivity and can compromise tissue integrity, while molecular methods like PCR are promising but require further validation due to potential false positives.

Conclusions:

• Even small metastases in SLNs are clinically significant and should not be overlooked.
• Current evidence supports the use of sensitive techniques like IHC for detecting occult metastases.
• Further research is needed to refine molecular techniques and establish definitive protocols for SLN examination to improve breast cancer patient outcomes.