Impact of Minimal Extrathyroidal Extension on Recurrence in Papillary Thyroid Carcinoma Measuring 4 cm or Less without Clinical Lymph Node Metastasis

Purpose: American Thyroid Association s guidelines (2015) recommend that papillary thyroid carcinomas (PTCs) ≤4 cm without extrathyroidal extension (ETE) and clinical lymph node metastasis (cLNM) can be treated by a unilateral procedure if a slightly higher risk of locoregional recurrence is accepted. The aim of the present study is to evaluate impact of minimal ETE (mETE) on locoregional recurrence in PTCs ≤4 cm without cLNM. Methods: The medical records of patients who underwent thyroidectomy for PTC ≤4 cm between January 1, 2007 and December 31, 2013 were retrospectively reviewed. Patients who had PTC with gross ETE and/or cLNM were excluded.-Patients with papillary thyroid microcarcinoma (PTMC) without ETE (group I; n=381) were compared with three other groups of patients: PTC 1&#8211;4 cm without ETE (group II; n=150); PTC ≤1 cm with mETE (group III; n=186); and PTC 1&#8211;4 cm with mETE (group IV; n=121). Mean follow-up period was 72.2±26.4 months. Results: Multiplicity, bilaterality, LNM, and total thyroidectomy were more common in group III and IV. Five-year disease-free survival (DFS) was 100%, 97.9%, 95.9%, and 94.9% in group I, II, III, and IV, respectively. DFS rates were significantly higher in group I compared to the other groups (P<0.01). There were no significant differences among group II, III, and IV. Conclusion: Compared to PTMC without ETE, mETE in PTC ≤4 cm without cLNM may be associated with more aggressive biological behavior and increased risk of recurrence, although the increments may be relatively small.