Sentinel node mapping in thyroid cancer: an overview

A combination of pre- and intraoperative techniques identifies sentinel lymph nodes in dogs with thyroid carcinoma: A pilot study

OBJECTIVE

The aim of this study was to develop and describe pre- and intra-operative sentinel lymph node (SLN) mapping techniques in dogs with thyroid carcinoma.

STUDY DESIGN

A prospective, pilot clinical trial was performed.

ANIMALS

Six client-owned dogs with unilateral thyroid carcinoma and no overtly metastatic locoregional lymph nodes (LNs) were enrolled.

METHODS

All dogs underwent preoperative indirect computed tomography (CT)-lymphography (CTL) with peritumoral iohexol injection and intraoperative SLN mapping with peritumoral injection of a visible dye (methylene blue [MB]) and near-infrared (NIR) fluorescent dye (indocyanine green [ICG]). Subsequent LN extirpation and routine thyroidectomy were performed. All excised tissues were evaluated histologically.

RESULTS

Pre- and intra-operative SLN mapping identified at least one SLN in all dogs. A median of one SLN (range, 1-2) was identified on both CTL and intraoperative SLN mapping. Identified SLNs included medial retropharyngeal, cranial deep cervical, and superficial cervical LNs. Variability between pre- and intra-operative SLN findings occurred in 3/6 dogs. A median of two LNs (range, 1-3) were extirpated for each dog. Metastatic carcinoma was diagnosed in extirpated LNs in 2/6 dogs and 3/12 extirpated LNs.

CONCLUSION

In this pilot study, preoperative CTL and intraoperative MB and ICG/NIR allowed for identification of SLNs in dogs with thyroid carcinoma.

CLINICAL SIGNIFICANCE

Sentinel lymph nodes were identified and extirpated using the described techniques, with nodal metastasis identified in a subset of these dogs due to SLN mapping. Large-scale, powered studies are needed to accurately determine the incidence and prognostic significance of nodal metastasis identified by SLN mapping and extirpation in dogs with thyroid carcinoma.

A multicenter prospective study of lateral neck lymph node mapping in papillary thyroid cancer

Background

Despite the high incidence of lateral neck lymph node (LN) metastasis in papillary thyroid cancer (PTC), the management of the lateral neck remains controversial. We aimed to map the draining LNs in the lateral neck using carbon nanoparticles and explore its potential in neck evaluation.

Methods

We conducted a multicenter, prospective study in PTC patients who had non-palpable yet suspicious metastatic lateral LNs on ultrasound and/or computed tomography (CT) but could not be confirmed by fine needle aspiration. Carbon nanoparticle suspension was injected peritumorally into the thyroid and modified lateral neck dissection was subsequently performed.

Results

A total of 154 patients were enrolled for analysis. And 5,070 lateral LNs were removed, of which 1,079 (21.3%) were dyed. The median of dyed LNs was 6 per case (range, 1-33). The distribution of dyed LNs in neck compartments was IV > III > IIA > IIB/V, independent of tumor size, location, multifocality or microscopic extra-thyroidal extension (ETE). Compared with undyed LNs, the probabilities of metastasis in dyed LNs were significantly increased in compartment III, IV, V, and II-V (III: 29.3% vs. 15.4%, P<0.001; IV: 26.3% vs. 14.5%, P<0.001; V: 16.7% vs. 3.3%, P=0.005; II-V: 26.3% vs. 10.0%, P<0.001). The relative risks of metastasis in dyed LNs compared with undyed LNs were 1.90, 1.82, 5.04 and 2.62 in compartment III, IV, V, and II-V, respectively.

Conclusions

It was the first prospective multicenter study to map the lateral neck LNs with carbon nanoparticles, which could help surgeons visualize the suspicious LNs during surgery. Instead of unguided LN biopsy, this method has a potential role in lateral neck assessment for indeterminate lateral LNs in PTC.