Prognostic Value of Extranodal Tumor Extension in Papillary Thyroid Carcinoma: Proposal for Upstaging of Cases with Extranodal Tumor Extension

Background Recently, we have created a revised version of the eighth edition of the tumor–node–metastasis classification for papillary thyroid carcinomas (PTCs) by subdividing the T4a (T4a1 [moderate] and T4a2 [significant]) and N (N1 [N ≤ 3 cm] and N2 [N > 3 cm]) classifications. This re-staging better stratified patient outcomes. In this study, we investigated the prognostic significance of extranodal tumor extension (LNEx) in PTC. Methods Five thousand six hundred and eighty-three patients with PTC surgically treated in Kuma Hospital were enrolled. We evaluated LNEx based on intraoperative findings. Results One hundred and twenty-seven patients (2%) displayed LNEx. In contrast to what we observed for extrathyroid extension, the prognostic value of LNEx did not change based on the organ that had been invaded, and we therefore analyzed LNEx patients as a single group. In patients aged 55 or older, LNEx independently affected patients’ prognoses, as did T4a2 and N2. The cancer-specific survival (CSS) of patients in Stage I but having LNEx demonstrated the similar prognosis to patients in Stage II. Further, in the subset analysis for Stage II patients aged 55 or older, LNEx had a significant prognostic value for CSS in both the univariate and multivariate analyses, as did N2. The CSS of Stage II patients aged 55 or older with LNEx did not differ from that of Stage III patients. Conclusions It is appropriate that, similar to T4a2 or N2 patients, LNEx-positive patients younger than 55 years in Stage I and those aged 55 or older in Stage II are re-staged to II and III, respectively.