Prevalence and prediction for malignancy of additional thyroid nodules coexisting with proven papillary thyroid microcarcinoma

Objective. To investigate the clinical efficacy of ultrasonographic (US) classification of additional thyroid nodules coexisting with proven papillary thyroid microcarcinoma (PTMC). Study Design. Historical cohort study. Setting. Tertiary care institution. Subjects and Methods. In addition to the prevalence of additional thyroid nodules based on an US classification, the diagnostic accuracy and predictive factors for malignancy were assessed in 300 nodules randomly selected from 300 patients with cytologically proven PTMC who underwent total thyroidectomy. Results. The most common thyroid nodules were ''indeterminate nodules,'' 68.0%, followed by ''probably benign nodules,'' 20.7%, and ''suspicious malignant nodules,'' 11.3%. For indeterminate nodules, the malignancy rate was 16.6% (34/204) with disregard to its location, either on the contralateral (15.1%, 16/106) or ipsilateral side (18.4%, 18/98) of the known PTMC (P = .53). According to univariate and multivariate analyses of clinical and US findings for predictive variables of malignancy in indeterminate nodules, hypoechogenicity was proven to be the sole predictive factor for malignancy (odds ratio 5.62, 95% CI, 2.29-13.72). Conclusion. US-based classification of additional thyroid nodules is a useful tool for decision making of the surgical extent in patients with a single PTMC.