Analysis of the Clinicopathologic Features of Papillary Thyroid Microcarcinoma Based on 7‐mm Tumor Size

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>We examined the clinicopathologic features of papillary thyroid microcarcinomas (PTMCs) measuring ≤7 mm and compared them with those of PTMCs >7 mm.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Between January 2007 and June 2009, a total of 275 patients with PTMCs underwent surgery. They were divided into two groups. Group I included patients with tumors ≤7 mm, and group II included those with tumors >7 mm but ≤10 mm. We compared the two groups’ clinicopathologic features.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Total thyroidectomy was more often performed in group II (<jats:italic>p</jats:italic> = 0.003). Central lymph node metastases were identified in 30.6% of the patients in group I and in 47.8% of the patients in group II (<jats:italic>p</jats:italic> = 0.005). A statistically significant difference between the two groups was also found for capsule invasion (<jats:italic>p</jats:italic> < 0.0001), extrathyroidal extension (<jats:italic>p</jats:italic> = 0.005), and lymphovascular invasion (<jats:italic>p</jats:italic> = 0.025). On the multivariate analysis, central lymph node metastasis was the only independent factor associated with tumor size.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>A PTMC ≤7 mm is less likely to have aggressive features, including central lymph node metastasis, capsule invasion, extrathyroidal extension, and lymphovascular invasion, than a PTMC >7 mm. Because the aggressiveness of PTMC was found mainly in the patients with tumors >7 mm, we think that a cutoff value of 7 mm may be considered the threshold of aggressiveness of PTMCs.</jats:p></jats:sec>