Extrathyroidal extension is not all equal: Implications of macroscopic versus microscopic extent in papillary thyroid carcinoma

Abstract

Extrathyroidal extension (ETE) is a risk factor for recurrence of papillary thyroid carcinoma (PTC). Although initial data supporting this was based on gross ETE noted at surgery, current treatment regimens group patients with microscopic ETE-identified only on histopathology-similarly to those with macroscopic (gross) ETE. This study was designed to assess the influence of microscopic ETE on disease recurrence. Retrospective analysis of 212 patients undergoing thyroidectomy for PTC between 1995 and 2004 with minimum 3-year follow-up was conducted. Of 212 patients, 71 had ETE; 32% were macroscopic and 68% microscopic. Patient demographics, tumor variables, and adjuvant therapy were similar between both ETE groups. Recurrence rates were 52% for macroscopic ETE, 21% for microscopic ETE, and 13% without ETE. On multivariate analysis, patients with macroscopic ETE had a 6.4-fold increased relative risk of recurrence compared with patients with microscopic ETE (P < .02; 95% confidence interval, 1.6-25.9) and a significantly decreased disease-free survival (DFS). Furthermore, patients with microscopic ETE had neither a significantly increased risk of recurrence nor different DFS compared with patients without ETE. Macroscopic ETE has a higher incidence of disease recurrence than microscopic ETE, implying they should be considered separately when devising adjuvant treatment regimens. The significance of microscopic ETE is undetermined.