Wolf in Sheep's Clothing: Papillary Thyroid Microcarcinoma in the US

Background: The presumptive overdiagnosis of papillary thyroid microcarcinoma (PTMC) has led to an emerging trend of less-extensive operation and an inclination toward active surveillance when possible. In this study, we aimed to examine the risk of advanced PTMC at presentation. Study Design: We conducted a retrospective analysis using the National Cancer Database (2010 to 2014). Patients with PTMC who underwent surgical intervention were included and patients with a history of any cancer were excluded. Results: A total of 30,180 adult patients with PTMC were identified; 5,628 patients (18.7%) presented with advanced features, including central lymph node (LN) metastasis (8.0%), lateral LN metastasis (4.4%), microscopic extrathyroidal extension (ETE; 6.7%), gross ETE (0.3%), lymphovascular invasion (LVI; 4.4%), and distant metastasis (0.4%). All of those features were associated with a significantly lower survival rate (p < 0.05 each) except for microscopic ETE and LVI. There was a significant interrelation among those features, distant metastasis was associated with central LN metastasis (odds ratio [OR] 2.44; 95% CI, 1.48 to 4.23; p < 0.001), lateral LN metastasis (OR 3.18; 95% CI, 1.77 to 5.71; p < 0.001), and gross ETE (OR 9.91; 95% Cl, 3.83 to 25.64; p < 0.001). In turn, nodal metastasis was associated with microscopic ETE (OR 4.23; 95% CI, 3.82 to 4.70; p < 0.001) and LVI (OR 7.17; 95% CI, 6.36 to 8.08; p < 0.001). Conclusions: PTMC could exhibit advanced features in 19% of patients who underwent operation and some of those, such as LVI and microscopic ETE, are undetectable with preoperative workup. Clinicians need to be cognizant of this considerable risk in the era of less-aggressive management of PTMC.