Rate of Extrathyroidal Extension and Lymph Node Metastases in Papillary Thyroid Carcinoma with Tall Cell Features
Frida Rosenblum Donath, Stefan Kraft, Justine A Barletta. Brigham and Women's Hospital, Boston, MA; Massachusetts General Hospital, Boston, MA
Background: While papillary thyroid carcinoma (PTC) is generally an indolent tumor, tall cell variant (TCV) is clinically more aggressive than classical PTC. For a tumor to be classified as TCV, at least 50% of the tumor must show tall cell histology. Although it has been recognized that a subset of PTCs have <50% tall cell histology, the significance of this finding has not been established. We designate tumors with <50% tall cell histology as having "tall cell features”. In our experience, similar to TCV, these tumors have a high rate of extrathyroidal extension (ETE) and lymph node (LN) metastases; however, these findings have never been formally evaluated. The aim of this study was to investigate the rate of ETE and LN metastases in PTCs with tall cell features and compare these rates to those of classical PTCs.
Design: We studied classical type PTCs and PTCs with tall cell features resected at our institution between 2010 and 2011. Tumors ≤1.0 cm and those with poorly differentiated or anaplastic components were eliminated from the study. For each case the following parameters were recorded: ETE, margin status, vascular invasion, LN status, number of positive LNs, size of the largest LN metastasis, and presence of extranodal extension (ENE).
Results: Our cohort included 99 tumors from 73 women and 26 men, with a mean age at resection of 45 years. Eighty-three (84%) tumors were classical and 16 (16%) had tall cell features. ETE was present in 20 (24%) classical PTCs and 11 (69%) tumors with tall cell features (p=0.0009). Although more tumors with tall cell features had a positive resection margin compared with classical PTCs (25% vs 8%, respectively), this difference did not reach statistical significance (p=0.075). Of cases with sampled LNs (78 cases, 79%), LN metastases were present in 37 (55%) classical PTCs and 10 (91%) tumors with tall cell features (p=0.04). For the tumors with tall cell features with positive LNs, the average number of LN metastases was 9, the mean size of the largest LN metastasis was 2.3 cm (range 0.1-5.5 cm), and the rate of ENE was 30%. In comparison, for the classical PTCs with positive LNs, the average number of LN metastases was 7, the mean size of the largest LN metastasis was 1.1 cm (range <0.1-4.5 cm), and the rate of ENE was 23%.
Conclusions: Our results demonstrate that PTCs with tall cell features have a significantly higher rate of ETE and LN metastases than classical type PTCs, suggesting that these tumors might, like TCV, pursue a more aggressive clinical course.
Tuesday, March 20, 2012 1:00 PM
Poster Session IV # 19, Tuesday Afternoon