Ill-defined edge on ultrasonographic examination can be a marker of aggressive characteristic of papillary thyroid microcarcinoma.

We have previously demonstrated that, although most papillary thyroid microcarcinomas (PMC) do not grow or grow only slowly, cases showing lateral node metastasis diagnosed by ultrasonography (US) show an aggressive characteristic associated with poor disease-free survival. In this study, we focused on two prominent U.S. features: tumor, edge definition and strong echoes. We investigated whether these findings reflect aggressive characteristics of PMC in a series of 155 cases. Poor edge definition was observed in 21.5% of patients, all of who showed worse disease-free survival (p = 0.0477) than those with a well-defined edge. Furthermore, this finding was directly linked to US-diagnosed lateral node metastasis (p = 0.0001). Strong echoes were observed in 63.9% of the cases, and fine strong echoes were seen in 25.2%. Cases demonstrating fine strong echoes tended to frequently show recurrence (p = 0.0902), and this finding was also significantly linked to US-diagnosed lateral node metastasis (p = 0.0494). These findings suggest that an ill-defined tumor edge is an important US feature of biologically aggressive PMC. We should carefully follow such patients, regardless of the therapeutic strategy, observation, or surgical treatment chosen.