Evaluation of predictive factors for lymph node metastasis in thyroid microcarcinoma: a two-year experience from two high-volume centers.

Papillary thyroid carcinoma incidence has increased rapidly in recent decades with microcarcinoma (maximum diameter ≤ 10 mm) representing the majority of new diagnoses. Being its prognosis excellent and mortality steady after surgery, some authors suggested active surveillance for microcarcinoma. However, microcarcinomas with lymph node metastasis at diagnosis are not uncommon. We aimed to assess independent risk factors for lymph node metastasis in patients with microcarcinoma. From January 2022 to December 2023, 234 papillary thyroid carcinomas from Fondazione Policlinico Universitario Campus Bio-Medico of Rome and Sant'Eugenio Hospital in Rome were retrospectively analyzed. Age, sex, maximum diameter, lymph node metastasis, Hashimoto's Thyroiditis, multifocality, capsule invasion and histological subtype were considered. Papillary carcinomas were stratified according to size and lymph node metastasis. Microcarcinoma were 145 (62.5%) and lymph node metastasis occurred in 16.6% of them. Multivariate regression revealed that young age (OR 0.90; 95% CI 0.86-0.95; p < 0.001) and capsular invasion (OR "presence" = 3.36; 95% CI 1.16-9.76; p = 0.026) resulted as independent risk factors for lymph node metastasis in patients with microcarcinoma. Being younger than 40 years old emerged as a significant cutoff for risk stratification of lymph node metastasis. Lymph node metastasis rate in microcarcinoma is considerable. A more careful evaluation is required for young patients with peripheral microcarcinoma where a more aggressive surgical approach (e.g. prophylactic central lymph node dissection) may be theorized. New tools are essential for the pre-surgical detection of high risk papillary thyroid microcarcinoma.