Clinical Implication of Mutifocality for Risk of Recurrence in Patients With Papillary Thyroid Carcinoma

Purpose Multifocality is frequently detected in papillary thyroid cancer (PTC). However, the prognostic significance of multifocality in PTC remains controversial. This study aimed to investigate the prognostic significance of multifocality in PTC. Methods We assessed 1,577 patients with PTC who underwent thyroid lobectomy from January 2008 to December 2016 at Seoul St. Mary’s Hospital (Seoul, Korea). The clinicopathological characteristics and long-term oncologic outcomes between multifocality and unifocality with PTC were compared. The mean follow-up duration was 97.2±20.0 months. Results Multifocality was observed in 290 (19.1%) patients. Compared with unifocality, multifocality had a significantly higher prevalence of extrathyroidal extension (ETE), vascular invasion, and more advanced N and TNM stages. The recurrence rate was significantly higher in multifocality than in unifocality (P=0.034). Multifocality was identified as a significant risk factor for disease-free survival (DFS) in the multivariate analysis (hazard ratio, 1.895; P=0.043). In the Kaplan-Meier analysis, a significant difference was noted in the DFS between the multifocality and unifocality groups (log-rank P=0.017). Conclusion Multifocality is associated with an increased risk of recurrence. This suggests that multifocality in PTC is a significant predictor of oncologic outcomes. Therefore, we suggest that patients with multifocality receive careful treatment from the initial evaluation to surgery and postoperative period.