Aggressive variants (AVs) of papillary thyroid carcinoma (PTC) - tall-cell variant, columnar-cell variant, diffuse-sclerosing variant, solid variant (SV), hobnail variant, oncocytic variant and Warthin-like variant of PTC are traditionally recognized to have poorer behavior and prognosis in comparison to classic (cPTC) subtype. SV PTC has been lately shown to be less aggressive than previously thought. The aim of this study was to determine clinical behavior and prognosis of AVs PTC in recent cases.

Using prospectively maintained institutional database all selected cases of AVs PTC treated from 2009 to 2019 were divided into 40 patients with SV PTC (intermediately aggressive group) and 40 patients of other AVs PTC (highly aggressive group) and matched for the tumor size. They were then individually matched for tumor size with the control group - 80 patients treated from cPTC.

Comparing AV PTCs to SV and cPTC, the AVs presented with higher rate of capsular invasion (62.5% vs. 15% vs 27.5%, p < 0.01), vascular invasion (40% vs. 2.5% vs. 15%, p < 0.01), lymph node metastases (32.5% vs. 2.6% vs. 5%, p < 0.01), extrathyroidal extension (32.5% vs. 7.7% vs 13.8%, p < 0.05) and periglandular tissue invasion (20% vs. 2.6% vs 6.3%, p < 0.05). For AVs PTC both the general and disease-specific survival was 88,9% and the disease-free survival was 80,6% for the mean follow-up period of 161.7 months.

The AVs PTC are notably more aggressive than cPTC and SV PTC, which should be considered in every-day patient treatment and subsequent follow up.