Predicting extrathyroidal extension in patients with papillary thyroid microcarcinoma according to a BRAF mutation

Objectives. The aim of this study was to evaluate the association between preoperative parameters and extrathyroidal extension (ETE) of papillary thyroid microcarcinoma (PTMC) according to the BRAF mutation and to evaluate the preoperative predictability of ETE. Methods. We analyzed the medical records of 332 patients with PTMC (140 in the BRAF– group and 192 in the BRAF+ group). The presence of ETE was subjected to a correlation analysis with age, sex, tumor size, clinical nodal status, and ultrasonography (US) findings. Among the US findings, the correlation between tumors and the thyroid capsule was categorized into four groups; US group A, intraparechymal; US group B, tumor abutting the capsule <50% of diameter; US group C, tumor abutting >50% of diameter; and US group D, tumor destroyed the capsule. The predictive value of ETE, including sensitivity, specificity, and positive and negative predictive values were evaluated. Results. Tumor size and US group were significantly correlated with gross ETE in the BRAF– and BRAF+ groups. Tumor size of 0.5 cm and US groups B and C in the BRAF– group were cutoff values for gross ETE, with a negative predictive value of 100%, whereas tumor size of 0.7 cm and US groups A and B in the BRAF+ group had negative predictive values of 92.4% and 100%, respectively. Conclusion. Excluding of ETE by US was categorized according to tumor size and US findings. A different categorization to exclude ETE is needed according to the BRAF mutation.