Preoperative detection and predictors of level V lymph node metastasis in patients with papillary thyroid carcinoma

Background: Papillary thyroid carcinoma (PTC) frequently metastasizes to regional lymph nodes. Metastasis to the posterior neck, level V, is uncommon, and level V lymphadenectomy may lead to spinal accessory nerve injury and associated postoperative morbidities. The aim of this study was to assess the diagnostic efficiency of preoperative ultrasonography and to identify predictors of level V metastasis in patients with PTC. Methods: This study involved patients with previously untreated PTC that had metastasized to the lateral neck, and who underwent total thyroidectomy with central and lateral neck dissection. Histopathological findings were compared with ultrasound results for various neck levels. Clinical and histopathological factors that predicted level V metastasis were identified. Results: Of 143 patients, 26 (18.2 per cent) had lymph node metastasis at level V. The sensitivity and positive predictive value of ultrasonography for level V metastasis were 46.2 and 30.0 per cent respectively. Univariable analysis showed that male sex, extranodal disease extension, a metastatic lymph node ratio in the ipsilateral lateral neck of more than 0.2, and simultaneous involvement of ipsilateral levels II-IV or level III were associated with ipsilateral level V metastasis. Multivariable analysis revealed an independent association between macroscopic extranodal disease extension and level V metastasis (odds ratio 26.05, 95 per cent confidence interval 5.63 to 120.56; P < 0.001). Conclusion: Preoperative ultrasonography frequently failed to detect level V metastasis in patients with metastatic PTC. Level V lymphadenectomy may be considered in patients with lymph node metastasis in the ipsilateral lateral neck with macroscopic extranodal extension.