Risk Factors of Metastatic Lymph Nodes in Papillary Thyroid Microcarcinoma

Papillary thyroid microcarcinoma (PTMC) usually has an indolent course, but some have worse prognostic factors, such as the presence of central (6.9%-51.5%) and lateral (3%-49.6%) lymph node metastases. The aim of this study is to analyze the factors associated with PTMC with metastatic lymph nodes and its long-term prognosis.

Retrospective study whose study population consists of patients with PTMC (size ≤1cm). Patients with previous thyroid surgery, other synchronous malignancies and ectopic location of the PTMC were excluded. Two groups were compared: PTMC without metastatic lymph nodes (group 1) and PTMC with metastatic lymph nodes (group 2). A multivariate analysis using a logistic regression model and a Kaplan-Meier survival analysis with log-rank test were performed.

Out of the 161 selected patients, 9.3% (n=15) had metastatic lymph nodes. Multifocality (OR 5.284, 95%CI 1.056-26.443; P=.043) and extrathyroidal extension (OR 7.687, 95%CI 1.405-42.050; P=.019) were associated with the presence of metastatic lymph nodes. In PTMC with metastatic lymph nodes, more aggressive treatments were performed: lymphadenectomy (4.8% vs. 100%; P<.001) and radioactive iodine (24.7% vs. 100%; P<.001). During a mean follow-up of 119.8±65 months, one recurrence was detected in group 2 (0% vs. 6.7%; P=.093). No patients died due to the disease.

Multifocality and extrathyroidal extension of PTMC were associated with the presence of metastatic lymph nodes. Metastatic PTMC, with more aggressive treatments, presents an excellent long-term prognosis.