Incidental papillary microcarcinoma of the thyroid—factors affecting lymph node metastasis

Background and aims Despite the overall excellent prognosis for patients with thyroid papillary microcarcinoma (PMC), these tumors are associated with lymph node metastasis. The aim of this study is to identify the rate of lymph node metastasis and evaluate the clinical and pathological factors affecting metastasis in thyroid PMC. Methods Among 475 patients with papillary thyroid carcinoma treated between 1990 and 2003, 81 patients (17%) were diagnosed as PMC and the records of these patients were evaluated retrospectively. Clinicopathologic features were evaluated by univariate and multivariate analyses. Results According to age, metastases, extent, and size risk definition, all patients were in low-risk group. Lymph node metastases were determined in 12.3% of patients. Mean follow-up was 7 years (range from 28 to 192 months). Ten-year disease-free and overall survival rates were 97 and 100%, respectively. Both multifocality and thyroid capsular invasion were found to be independent risk factors for lymph node metastasis by multivariate analysis. Conclusion Patients with thyroid PMC in low-risk group with multifocal tumors and with capsule invasion may have increased risk of lymph node metastasis, and must be considered in follow-up of the patients who have these factors.