Background: Preoperative prediction of lateral lymph node metastasis (LNM) is important to prevent recurrence; however, there are few published data in predicting factors of lateral LNM before surgery. The present study investigated the factors affecting LNM in patients with papillary thyroid microcarcinoma (PTMC). Methods: A retrospective cohort study was conducted with data obtained from 671 patients with PTMC between 2004 and 2006. We reviewed the clinical, ultrasound (US), and pathology records of patients and analyzed the association between lateral LNM and clinical factors, US features of PTMC, and pathologic features. Results: The rate of lateral LNM was 3.7% in 671 PTMCs. We found a statistically significant association between lateral LNM and US features of PTMC (upper pole location, contact of >25% with the adjacent capsule, and presence of calcifications), and pathologic features (central LNM) in multivariate analysis (P < .05). The odds ratios of statistically significant factors were 4.7 (95% confidence interval [95% CI], 1.8-12.6), 10.8 (95% CI, 3.3-34.6), 4.8 (95% CI, 1.6-13.7), and 6.9 (95% CI, 2.4-20) at upper pole location, contact of >25% with the adjacent capsule, presence of calcifications on US, and pathologic central LNM, respectively. Conclusions: In patients with PTMC, independent factors in predicting lateral LNM were US features of PTMC (upper pole location, >25% contact with the adjacent capsule, and presence of calcifications) and pathologic features (central LNM). When these US features are detected on preoperative US, lateral neck nodes should be meticulously evaluated by a multimodal approach.
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