Clinical and Pathologic Predictors of Lymph Node Metastasis and Recurrence in Papillary Thyroid Microcarcinoma

Background: The treatment for patients with papillary thyroid microcarcinoma (PTMC) is controversial because PTMC is often found incidentally and its prognosis is very good. Lymph node metastasis (LNM) is one of the main predictors of recurrence and survival. This retrospective study aimed to identify clinical and pathologic factors that increase the risk of metastasis or recurrence, in order to isolate clinically unfavorable PTMCs to help guide therapy. Methods: Clinical and pathologic data were collected from 273 patients diagnosed with PTMC at The University of Chicago Medical Center between 2000 and 2011. Data points included age, sex, race/ethnicity, tumor size, multifocality, thyroiditis, extrathyroidal extension (ETE), surgical margins, preoperative clinical suspicion of cancer, central/lateral lymph nodes removed and lymph nodes with metastatic carcinoma, treatment, local recurrence, distant recurrence, and survival. Results: Multivariate logistic regression showed that age <45 years (odds ratio [OR] = 3.565 [confidence interval (CI) 1.137-11.177]), multifocality (OR = 3.556 [CI 1.066-11.855]), and ETE (OR = 4.622 [CI = 1.0680-20.011]) significantly increased the risk of central LNM (CLNM). However, sex, size of tumor, thyroiditis, positive margins, and clinical suspicion were not correlated with an increased risk for CLNM. Multivariate logistic regression showed that only ETE (OR = 16.066 [CI 1.850-139.488]) significantly increased the risk of lateral LNM. In the cohort of 202 patients with follow-up data, only six recurred. Median time to recurrence was approximately 12 months (range 3.5-120 months), and median follow-up was 42 months. No patient had distant metastasis, and no patients died. Conclusions: PTMC is an indolent disease, but does pose a risk for LNM and local recurrence. More aggressive treatment or more frequent follow-up could be considered for patients with unfavorable features (age <45 years, multifocality, ETE), especially in the setting of involved lymph nodes at the time of surgical resection, as these patients may be at an increased risk for recurrence.