Risk Stratification in Papillary Thyroid Microcarcinoma: Clinical Features Predicting Multifocality, Lymph Node Metastasis, and Recurrence - A Retrospective Cohort Study.

Purpose: Papillary thyroid microcarcinoma (PTMC, ≤1 cm) has risen sharply in incidence, comprising nearly half of papillary thyroid carcinoma cases. This study assessed clinical features and risk factors for multifocality, nodal metastasis, and recurrence to inform treatment and risk stratification. Patients and Methods: We retrospectively analyzed 418 patients diagnosed with PTMC at Chang Gung Memorial Hospital between 2005 and 2015. Patients with incomplete data, initial distant metastasis, or lost to follow-up were excluded. Clinical, pathological, and treatment data were reviewed. Risk factors were identified using multivariate logistic regression analysis. Sensitivity analysis was performed on the total thyroidectomy subgroup to address potential selection bias. The study was IRB-approved and informed consent was waived due to its retrospective nature. Results: Among 418 patients (75 males, 343 females; median age 47 years), the median tumor size was 6.0 mm. Multifocal PTMC occurred in 32.1% of patients and was significantly associated with larger tumor size (p < 0.001) and lymphovascular invasion (p < 0.001). Cervical lymph node metastasis was observed in 11.5% of patients and was linked to male sex (OR: 3.27, p = 0.006), non-incidental findings (OR: 8.38, p < 0.001), multifocality (OR: 3.13, p = 0.047), and lymphovascular invasion (OR: 709.01, p < 0.001). Sixteen patients (3.8%) experienced recurrence, which was significantly associated with prior lymph node metastasis (OR: 6.24, p = 0.011). The overall survival rate was 97.6%. Conclusion: PTMC is usually indolent, but male gender, non-incidental findings, multifocality, and lymphovascular invasion indicate higher risk. These mainly histopathological factors can guide management and are particularly relevant when evaluating alternatives such as radiofrequency ablation.