Predictive factors for occult contralateral carcinoma in patients with unilateral papillary thyroid microcarcinoma by preoperative ultrasonographic and pathological features.

Background: The surgical extent and indication for treatment in patients with papillary thyroid microcarcinoma (PTMC) remain a controversial issue. The aim of this study was to investigate the predictive factor for contralateral occult carcinoma in patients with unilateral PTMC by preoperative ultrasonographic and pathological features.

Methods: Of the total patients who underwent thyroidectomy, 455 patients with PTMC confined to one unilateral lobe as diagnosed using preoperative ultrasonography (US) were enrolled in the study. Occult contralateral carcinoma was defined as tumor foci in the contralateral lobe that was not detected preoperatively, but was detected pathologically. All patients underwent preoperative US review to investigate the US features of PTMC such as laterality, location, size, internal component, echogenicity, margin, calcification shape, multifocality, bilaterality, extrathyroidal extension, and location with respect to the trachea. Clinicopathological data were also analyzed.

Results: Of the total of 455 patients who underwent total thyroidectomy for preoperatively detected unilateral PTMC, 71 patients (15.6 %) had contralateral occult carcinoma. Clinicopathological characteristics did not significantly differ between patients with and without contralateral occult carcinoma. Multivariate analysis showed that the absence of a well-defined margin and the presence of a probably benign nodule in the contralateral lobe were independent predictive factors for contralateral occult carcinoma in patients with unilateral PTMC in preoperative US images.

Conclusion: We demonstrated that an absence of a well-defined margin and the presence of a probably benign nodule in the contralateral lobe were independent predictive factors for contralateral occult carcinoma in patients with unilateral PTMC in preoperative US. The prediction of contralateral occult carcinoma in unilateral PTMC using preoperative US features could be useful for determining the optical extent of surgery.