The sentinel lymph node biopsy technique in papillary thyroid carcinoma: The issue of false-negative findings

Background: The management of papillary thyroid carcinoma (PTC) is changed after introduction of sentinel lymph node biopsy (SNB) technique for nodal staging. Some debate still surrounds the accuracy of this procedure in terms of wide heterogeneity of sentinel lymph node detection and false-negative findings. Aim: to identify the key issues which make it difficult the usefulness of SNB in PTC. Methods: A comprehensive computer literature search of meta-analyses published in PubMed/MEDLINE and Cochrane library database until June 30, 2019 was conducted. We used a search algorithm based on this combination of terms: (i) “thyroid neoplasm” or “thyroid cancer” or “thyroid carcinoma” or “thyroid malignancy” or “meta-analysis” or “systematic review”) AND (ii) “sentinel lymph node biopsy”. Results: Comparing 4 written meta-analyses published in the literature, the diagnostic performance of SNB technique in PTC has been summarized. Relatively high false-negative rates (FNR) were reported for each SNB methods: vital-dye (VD: 12.7%; 7%; 0–38%), 99mTc-nanocolloid planar lymphoscintigraphy with the use of intraoperative hand-held gamma probes (LS: 11.3%; 16%; 0–40%), combined LS with VD (LS+VD: 0%; 0–17%), LS with the additional contribution of preoperative SPECT/CT (7–8%). Conclusion: Evidence-based data about the diagnostic performance of SNB in PTC are increasing. The nuclear medicine community should reach a consensus on the operational definition of the SLN to better guide the surgeon in identifying the lymph nodes most likely contain metastatic cells. Standardization of SLN identification, removal and analysis are required.