Papillary Carcinoma of Thyroid Nodule if Located in Isthmus Is Associated with Greater Disease Progression: a Systematic Review and Meta-analysis

The aim of this study was to evaluate the clinicopathologic characteristics and pattern of lymph node (LN) metastasis in papillary thyroid cancer (PTC) located in the isthmus. A systematic review of the relevant electronic databases was conducted between January 2000 and December 2019, including Pubmed, Web of Science, and the China Journal Net. Outcomes of interest included gender, age, tumor size, multifocality, capsule invasion, extrathyroidal extension, and lymph node metastasis. We calculated the pooled odds ratios (ORs) with 95% confidence intervals (CIs) for each study using a random or fixed effect model. Nine studies with a total of 4541 patients were included. Patients with isthmic PTC were 565 (12.4%). Our meta-analysis revealed that there was a significant association between the isthmus location and multifocality (OR = 1.50; 95% CI = 1.18–1.90), capsule invasion (OR = 1.53; 95% CI = 1.17–1.99), extrathyroidal extension (ETE) (OR = 1.95; 95% CI = 1.34–2.86), and central LN metastasis (OR = 1.53; 95% CI = 1.17–1.99). For patients with solitary nodule, our meta-analysis illustrated that there was a significant association between the isthmus location and ETE (OR = 1.65; 95% CI = 1.11–2.46), and central LN metastasis (OR = 2.50; 95% CI = 1.82–3.44). However, the meta-analysis suggested that there was no correlation between the isthmus location and lateral LN involvement (OR = 1.04; 95% CI = 0.58–1.87). PTCs located in the isthmus were associated with multifocality, capsule invasion, ETE, and more likely to involve the central lymph node.