Extrathyroidal Extension is Not All Equal: Implications of Macroscopic Versus Microscopic Extent in Papillary Thyroid Carcinoma

Background: 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.

Methods: Retrospective analysis of 212 patients undergoing thyroidectomy for PTC between 1995 and 2004 with minimum 3-year follow-up was conducted.

Results: 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.

Conclusion: 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.