Evaluation of epithelial-to-mesenchymal transition and Ki-67 index in aggressive papillary thyroid cancer

Objectives: The present study aims to characterize immunohistochemical features of markers associated with Epithelial-Mesenchymal Transition (EMT) and proliferative activity that could lead to death in Papillary Thyroid Cancer (PTC).

Methods: Clinical data and tumor material were retrospectively collected. The patients were separated into death from PTC (Group 1), metastatic cases with indolent behavior (Group 2) and non-metastatic indolent PTC (Group 3). Immunohistochemical assessment of E-cadherin, β-catenin, Vimentin, ZEB-1 and Ki-67 was performed in each tumor and a semiquantitative estimation of the percentage of expression was fulfilled on the best marking area at high of the tumor invasion front.

Results: 31 patients were included, 15 that died from PTC (Group 1), 6 in Group 2 and 10 in Group 3. The proliferative marker Ki-67 showed a significant difference in its expression in the tumor invasion front between the groups, specifically between groups 1 and 3 (p = 0.006). On the other hand, EMT-related immunohistochemical markers did not show significant difference in their percentage of expression, since loss of E-cadherin, β-catenin and Vimentin was observed in most cases at the invasion front.

Conclusion: Patients that died from PTC had a significantly higher Ki-67 labelling index compared to patients with indolent disease (cutoff of 11%). Ki-67 may have a role as a prognostic marker and could be considered for routine use in PTC.