Lymph node metastases in clinically N0 patients with papillary thyroid microcarcinomas - a single institution experience

PURPOSE: To register the frequency of central and lateral lymph node metastases (LNMs) from papillary thyroid microcarcinomas (PTMCs), and to assess whether sentinel lymph node (SLN) biopsy of the lateral compartment is an accurate technique to select patients with true positive but clinically negative lymph nodes for one-time selective lateral neck dissection (sLND). The correlation between tumor characteristics (size, multifocality, bilaterality, capsular invasion) and LNMs was analyzed.

METHODS: During a 10-year-period (2004-2013), 111 clinically N0 patients with PTMCs had total thyroidectomy, central neck dissection and SLN biopsy of the lateral neck compartment in our institution. SLN mapping was performed by subcapsular injection of 0.2 to 0.5ml of 1% methylene blue dye. If SLNs were positive on frozen section, one-time sLND was done.

RESULTS: Forty per cent of PTMCs were multicentric. LNMs were detected in 25% of the patients and isolated central LNMs were found in 18% of the patients. Lateral LMNs were present in 7% of the patients, of which 4% were isolated, skip LNMs. All these patients had therapeutic sLND. Specificity and sensitivity of SLN biopsy were 100% and 57%, positive and negative predictive values were 100% and 97%, respectively. Method's accuracy was 97%.

CONCLUSIONS: SLN biopsy of the lateral neck compartment is more precise than physical examination and ultrasonography for detection of lateral LNMs in clinically N0 patients with PTMCs. Intraoperative assessment of lateral lymph nodes (SLNs) provides one-time therapeutic dissection for patients with occult LNMs at initial operation, reducing the need for additional operations. This method provides appropriate disease staging and optimizes treatment.