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A combination of pre- and intraoperative techniques identifies sentinel lymph nodes in dogs with thyroid carcinoma: A
Maureen A Griffin1, Deanna R Worley2, Brian K Flesner1
1Department of Clinical Sciences and Advanced Medicine, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, USA.
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.
