Nodal metastases in papillary thyroid microcarcinoma: prevalence and risk factors in 311 patients

Papillary thyroid microcarcinoma (PTMC) is generally considered low risk due to its favourable prognosis; however, in some cases, it presents aggressive features such as lymph node metastasis and extrathyroidal extension (ETE). The aim of this study was to investigate the pathological factors that influence prognosis in PTMC with the purpose of refining risk stratification based on our cohort of 311 cases. We performed a retrospective analysis based on anonymous data from 311 PTMC samples (tumours ≤ 1.0 cm in size) collected between 2016 and 2024. We examined several variables, including gender, histological subtype, tumour size, ETE, lymph node metastasis, and thyroiditis. The evaluations followed the eighth edition of the American Joint Committee on Cancer (AJCC) staging system. We used Pearson's chi-square test for univariate analysis and binary logistic regression for multivariate analysis. A p-value less than 0.05 was considered statistically significant. In our cohort, 45 patients (14.5%) had lymph node metastases. Male sex (OR = 3.3132; 95% CI = 1.5554-7.0574; p = 0.002), age < 45 years (OR = 2.4974; 95% CI = 1.2228-5.1006; p = 0.012), multicentricity (OR = 2.9351; 95% CI = 1.4314-6.0182; p = 0.003) and vascular invasion (OR = 3.5184; 95% CI = 1.3044-9.4905; p = 0.013) are found to be independent risk factors for lymph node metastases. The tall cell histological subtype (OR = 3.897; 95% CI = 1.6649-9.122; p = 0.002) emerged as an independent predictor of ETE. Although PTMC is commonly considered an indolent neoplasm, some cases may present aggressive features that require careful prognostic evaluation. The identification of independent risk factors may improve clinical decision-making and therapeutic strategies for patients with PTMC.