Sentinel node mapping and biopsy in thyroid cancer: a surgical perspective

The clinical role of sentinel node biopsy (SNB) in thyroid cancer remains an open matter in literature. The main reason of this fact is that nodal disease is considered a non-relevant prognostic factor by some authors in differentiated thyroid cancer (DTC). Aim of this study was to investigate the efficacy of radiocolloid lymphoscintigraphy and of hand held gamma probe procedure for SNB in patients with DTC and its potential clinical role. Forty-one consecutive pts with a small thyroid nodule highly suspected for malignancy at fine-needle aspiration cytology (FNAC) and without clinical and ultrasonographic (US) evidence of lymph node involvement entered the study. All patients underwent lymphoscintigraphy 3 hours before intervention using a 99mTc-nanocolloid solution. One single intratumoral injection of 4-9 MBq in 0.1-02 ml normal saline was obtained under US-guidance followed by a dynamic lymphoscintigraphy. After total thyroidectomy central and lateral compartments of the neck were scanned with a hand held gamma probe. The hottest node and any lymph node with a count rate of more than 10% of the hottest node were removed. SLNs were sent to frozen section analysis and a surgical enlargement of corresponding compartment was performed when at least one SLN was positive at histology. Preoperative lymphoscintigraphy was able to identify one node in six cases, two nodes in five cases, three nodes in 14 cases, four or more nodes in 16 cases. A papillary thyroid carcinoma (PTC) was diagnosed in 39 cases, a mixed papillary-medullary carcinoma in one case and a micro-follicular adenoma in one case. In 21/40 patients (pts) positive lymph nodes were found: in 16/21 patient one node showed micrometastasis only, in 5/21 patients more nodes were metastatic. In particular in 11 cases the first hottest node was involved (true SLN), in 10 cases a second or third hot lymph node was involved. In our preliminary experience lymphoscintigraphy with 99mTc-nanocolloid resulted highly sensitive: in fact at least one lymph node was visualized in all cases and the surgeon was able to detect by means of hand held probe during intervention al least one hot SLN in all cases. In 21/40 pts (more than 50% of cases) metastatic lymph nodes were found despite preoperative clinical and US examination negative for lymph node involvement. In prospective SLN technique might be proposed as a relevant tool in lymphoadenectomy decision in DTC patients with a small tumor.