Clinicopathologic characteristics of papillary thyroid carcinoma, tall cell subtype and subtype with tall cell...

Papillary thyroid carcinoma (PTC) is categorized into various subtypes, including classic PTC (cPTC) with 0 % tall cell morphology, PTC with tall cell features (PTCtcf) with >0 but <30 % tall cells, and tall cell subtype of PTC (tcsPTC) having ≥30 % tall cells. This case-cohort study investigated the clinicopathologic characteristics of cPTC, PTCtcf, and tcsPTC. Patients with. tcsPTC subtype were older (mean 50.2 years) than patients with cPTC (42.0 years) and PTCtcf (45.6 years). tcsPTC subtype presented with more advanced tumor stages than cPTC, indicating more aggressive tumor behavior. The frequency of extra-thyroidal extension in tcsPTC (60.1 %) and PTCtcf (39.7 %) was higher than in cPTC (23.6 %). Angioinvasion was more frequent in tcsPTC (15.1 %) than cPTC (7.6 %). Positive margins were more common in PTCtcf (12.4 %) and tcsPTC (23.9 %) than cPTC (4.9 %). tcsPTC and PTCtcf had more tumor foci than cPTC. Recurrent or persistent disease occurred more frequently in PTCtcf (13.2 %) and tcsPTC (6.7 %) compared with cPTC (1.5 %). Kaplan-Meier survival analysis demonstrated that all tcsPTC tumors and those tcsPTC tumors ≤1 cm had worse overall and disease-unrelated survival outcomes compared with cPTC, which was mostly due to second non-thyroid tumors. There were no differences in disease-related survival among the 3 PTC subgroups possibly due to efficacy of radioactive iodine therapy more frequently used for treating PTCtcf and tcsPTC compared with cPTC. In conclusion, the findings highlight the aggressive nature of tcsPTC and PTCtcf and emphasize the value of histologic subtyping in guiding management of thyroid carcinoma.