Comparison of the clinicopathological features and oncologic outcomes of the classic papillary thyroid carcinoma with tall cell features and tall cell variant.

Abstract

The tall cell variant (TCV) of papillary thyroid carcinoma (PTC) (TCVPTC) is the most common aggressive variant of PTC. Classic PTC with tall cell features (TCF) is defined as PTC with noticeable tall cells but the percentage of these cells is lower than that required for the diagnosis of TCVPTC. We aimed to investigate the potential differences between TCVPTC and classic PTC with TCF with respect to clinicopathological characteristics and oncologic outcomes. We retrospectively assessed 509 patients with TCVPTC or classic PTC with TCF who underwent thyroid surgery between January 2013 and December 2018 at the Seoul St. Mary's Hospital (Seoul, Korea). Clinicopathological characteristics and oncologic outcomes between TCVPTC and classic PTC with TCF were compared in terms of disease-free survival (DFS). The mean follow-up duration was 70.7±21.7 months. The mean tumor size was significantly larger in the TCVPTC group. There was no significant difference between the TCVPTC and classic PTC with TCF groups with respect to DFS. Tumor size >2 cm [odds ratio (OR), 1.922; P=0.019], bilaterality (OR, 1.668; P=0.030), extrathyroidal extension (ETE) (OR, 2.352; P=0.002), and lateral LN metastasis (OR, 1.700; P=0.045) were significantly associated with TCVPTC compared with classic PTC with TCF. TCVPTC and classic PTC with TCF have similar clinicopathological characteristics and oncologic outcomes. Therefore, we suggest a potential re-classification of classic PTC with TCF from low-risk to intermediate-risk category in the American Thyroid Association (ATA) risk stratification system.