Prognostic Factors Affecting Neck Lymph Node Recurrence and Distant Metastasis in Papillary Microcarcinoma of the Thyroid: Results of a Study in 445 Patients

Background: The management of thyroid papillary microcarcinoma (PMC) is controversial. Total thyroidectomy, thyroid lobectomy/isthmectomy, and even no treatment have been proposed. We investigated the clinical course and prognostic factors for disease recurrence and distant metastasis in 445 patients with PMC. Methods: Data from 445 patients diagnosed with PMC in the period from 1978 to 2003 were reviewed and analyzed. Total thyroidectomy was performed in 404 patients and loboisthmusectomy in 41. Neck dissection took place in 226 patients (49.7%), with 166 of only the central compartment and 60 of both the central and lateral compartments. Radioiodine (I-131) ablation treatment was given to 389 patients. Results: Median tumor size was 7mm (range 1-10mm). PMC was multifocal in 156 cases (35%) and bilateral in 60 cases (13.5%). Extrathyroidal tumor extension (pT3) and neck lymph node metastasis (pN1) were present in 133 (30%) and 182 (40.9%) patients, respectively. Capsular invasion without extrathyroidal tumor extension was observed in 39 (8.7%) patients. Mean follow-up was 5.3 (range 1-26) years. Seventeen (3.8%) patients had recurrence or persistence of disease: neck recurrence (NR) in 12 (2.7%), distant metastasis (DM) in four (0.9%), NR + DM in one (0.2%). One patient (0.2%) died of the disease. Capsular invasion, extrathyroidal tumor extension (pT3), and neck lymph node metastasis at presentation (pN1) were the only independent risk factors for NR and/or DM occurrence (p < 0.05). Patients not showing these features, who were treated with loboisthmusectomy only, never experienced disease recurrence. Conclusion: Total thyroidectomy seems advisable in PMC with extrathyroidal extension and neck lymph node metastasis at presentation. Capsular invasion without extrathyroidal extension may suggest aggressive tumor behavior and require radical treatment.