Do aggressive variants of papillary thyroid carcinoma have worse clinical outcome than classic papillary thyroid carcinoma?

Objective: Evidence for unfavorable outcomes of each type of aggressive variant papillary thyroid carcinoma (AV-PTC) is not clear because most previous studies are focused on tall cell variant (TCV) and did not control for other major confounding factors contributing to clinical outcomes. Design: Retrospective cohort study. Methods: This study included 763 patients with classical PTC (cPTC) and 144 with AV-PTC, including TCV, columnar cell variant (CCV) and hobnail variants. Disease-free survival (DFS) and dynamic risk stratification (DRS) were compared after two-to-one propensity score matching by age, sex, tumor size, lymph node metastasis and extrathyroidal extension. Results: The AV-PTC group had significantly lower DFS rates than its matched cPTC group (HR = 2.16, 95% CI: 1.12-4.16, P = 0.018). When TCV and CCV were evaluated separately, there was no significant differences in DFS and DRS between patients with TCV (n = 121) and matched cPTC. However, CCV group (n = 18) had significantly poorer DFS than matched cPTC group (HR = 12.19, 95% CI: 2.11-70.33, P = 0.005). In DRS, there were significantly more patients with structural incomplete responses in CCV group compared by matched cPTC group (P = 0.047). CCV was an independent risk factor for structural persistent/recurrent disease in multivariate analysis (HR = 4.28; 95% CI: 1.66-11.00, P = 0.001). Conclusions: When other clinicopathological factors were similar, patients with TCV did not exhibit unfavorable clinical outcome, whereas those with CCV had significantly poorer clinical outcome. Individualized therapeutic approach might be necessary for each type of AV-PTCs.