Lymphoscintigraphic and intraoperative detection of sentinel lymph node in papillary thyroid cancer

Aim: We applied the Sentinel Lymph Node (SLN) technique using the lymphoscintigraphy (LS) preoperatively and the gamma-probe (GP) intraoperatively to evaluate the feasibility, safety and accuracy of the SLN in Papillary Thyroid Cancer (PTC).Materials and Methods: Of 84 patients with PTC, we enrolled 40 with at least one year follow-up from thyroidectomy. The day before surgery, they were submitted to US guided peri-tumoral injection of about 120 MBq of 99mTc- Nanocoll®. The LS was performed 30-180 min after the injection. Then, a thyroidectomy was done. In 25 patients, after removal of any SLN, an average of 6 lymph nodes were excised in the SLN compartment. The SLN was sent separately with other lymph nodes to the pathologist for histopathological analysis.Results: The SLN was identified in all patients. The SLN localization side by the GP was: central compartment in 25 patients (64%), laterocervical compartment on the same side of the tumor in 12 patients (31%), laterocervical compartment on the opposite side of the tumor in 2 patients (5%). In 1 cases the metastatic lymph nodes were peri-thyroid, so we removed them with thyroidectomy. Of the 39 patients in whom the SLN was detected intraoperatively, 30 patients (75%) had no SLN metastases, 8 patients (20%) had SLN metastases, and one patient (2.5%) had SLN micrometastases on final pathology. In 4 patients (10%), no SLN metastases were detected, but other lymph nodes belonging to the SLN compartment were positive for cancer. One year follow-up was negative for disease in all cases.Conclusions: The SLN technique identifies the lymphatic drainage in PTC; thus, by removing both the SLN and all other lymph nodes belonging to the same compartment, all possible metastatic lymph node should have been resected. Our study shows that the SLN technique is accurate because positive localization of SLN in 97.5% of cases and feasible because it is repeatable. Moreover, the SLN technique allows to guide a target lymph node biopsy, to identify lymph nodes metastases not evaluable on preoperative imaging studies and to identify micrometastases. Locoregional lymphoadenectomy on the same side of the SLN represent a rationale treatment for lymph nodes in PTC. This attitude may represent a “golden mean” between central and laterocervical lymphoadenectomy and postoperative radioiodine therapy alone, allowing better prognostic definition, with no increase in morbidity.