The importance of sentinel lymph node diagnostic biopsy from the lateral neck compartment in the surgical treatment of papillary thyroid cance.

[OBJECTIVES] The aim of our study is to determine whether mapping the lymphatic drainage and diagnostic excision of lymph nodes from lateral neck compartment is able to detect ultrasound unknown metastases in this compartment early and thus favorably affect the prognosis of patients with papillary thyroid cancer (PTC).

[BACKGROUND] Lymph node involvement in the lateral neck compartment is seen in 30-60 % of patients with PTC at the time of diagnosis and affects the prognosis of patients in terms of disease recurrence.

[METHODS] From June 2012 to December 2016, 154 patients with no evidence of lateral nodal involvement on imaging studies were treated with total thyroidectomy and central comparment neck dissection. A volume of 0.2 ml of Patent Blue dye was applied in the upper half of the thyroid gland with subsequent exposure of lymphatic drainage in the lateral compartment and 2-3 sentinel lymph nodes (SLN) were removed for frozen section (Group 1). In case of metastatic involvement, a lateral comparment neck dissection was performed. The reference groups were composed of a set of patients without detected lymphatic drainage (Group 2) and a set of patients who underwent lateral compartment neck dissection for preoperatively detected metastases in the lymph nodes (Group 3). The biochemical, structural and overall persistence of the disease at the time of administration of adjuvant radioiodine ablation was evaluated.

[RESULTS] The SLN identification rate was 95.45 %. In Group 1, a total of 32 patients had a positive SLN. Out of these, 24 patients had positive SLNs based on the analysis of frozen section, while in 8 patients, the positive diagnosis was confirmed through definitive histology. The comparison of data from the entire follow-up period in all three groups of patients revealed statistically significant differences in persistence of disease, namely in favor of Group 1. The percentage of reoperations for persistence and recurrence of disease was significantly lowest in Group 1 (2.04 %) compared to Groups 2 and 3 (6.94 % and 45.45 % respectively).

[CONCLUSION] The method is safe and sensitive for detecting unknown lymph node metastases in the lateral neck compartment, and may facilitate a decision to perform accurate surgical treatment of patients with PTC (Tab. 4, Fig. 2, Ref. 38).