Detection of Tumor Multifocality Is Important for Prediction of Tumor Recurrence in Papillary Thyroid Microcarcinoma: A Retrospective Study and Meta-Analysis

Background: The clinicopathological characteristics and conclusive treatment modality for multifocal papillary thyroid microcarcinoma (mPTMC) have not been fully established. Methods: A retrospective study, systematic review, and meta-analysis were conducted to elucidate the clinicopathological significance of mPTMC. We investigated the multiplicity of 383 classical papillary thyroid microcarcinomas (PTMCs) and the clinicopathological significance of incidental mPTMCs. Correlation between tumor recurrence and multifocality in PTMCs was evaluated through a systematic review and meta-analysis. Results: Tumor multifocality was identified in 103 of 383 PTMCs (26.9%). On linear regression analysis, primary tumor diameter was significantly correlated with tumor number (R-2 = 0.014, p = .021) and supplemental tumor diameter (R-2 = 0.117, p = .023). Of 103 mPTMCs, 61 (59.2%) were non-incidental, with tumor detected on preoperative ultrasonography, and 42 (40.8%) were diagnosed (incidental mPTMCs) on pathological examination. Lymph node metastasis and higher tumor stage were significantly correlated with tumor multifocality. However, there was no difference in nodal metastasis or tumor stage between incidental and non-incidental mPTMCs. On meta-analysis, tumor multifocality was significantly correlated with tumor recurrence in PTMCs (odds ratio, 2.002; 95% confidence interval, 1.475 to 2.719, p < .001). Conclusions: Our results show that tumor multifocality in PTMC, regardless of manner of detection, is significantly correlated with aggressive tumor behavior.