Does Extracapsular Extension Impact the Prognosis of Papillary Thyroid Microcarcinoma?

Extracapsular (EC) extension is a pejorative factor in papillary thyroid carcinoma (PTC). However, the impact of EC extension in microcarcinoma (micro-pT3) remains controversial, and all pT3 patients are currently considered to be at high risk of recurrence. This study sought to determine the risk of recurrence in patients with micro-pT3 and to compare their outcomes with other pT3 (macro-pT3) and low-risk patients. All consecutive patients who received surgery for PTC in our department from January 1978 to December 2011 were included in this study. We compared three patient groups: micro-pT3 (a parts per thousand currency sign10 mm with EC extension), macro-pT3, and low risk, including pT1a-b s N0-x, pT1a-b m N0-x, and pT2 N0-x. Total thyroidectomy was performed with lymph node (LN) dissection in most cases, and radioiodine therapy was administered as needed. The median follow-up period was 6.7 years. A total of 2,482 patients were included in this study, including 178 micro-pT3 patients, 533 macro-pT3 patients, and 1,771 low-risk PTC patients. Recurrence was documented in 14 (7.9 %) micro-pT3 patients, 124 (23.3 %) macro-pT3 patients, and 36 (2 %) low-risk PTC patients. The micro-pT3 patients with LN metastases (N1) demonstrated a higher recurrence rate than the N0-x patients (14.8 vs. 4.8 %; p < 0.01), whereas the risk of recurrence among the T2 N0-x (5 %) and micro-pT3 N0-x (4.8 %) patients was similar (p = 0.95). Micro-pT3 N1 patients are at high risk of recurrence and should be treated aggressively. Because the outcomes of the micro-pT3 N0-x patients were similar to those of the low-risk PTC patients (pT2 N0-x), we suggest that micro-pT3 N0-x should be treated in a similar manner, with low-dose iodine-131 and recombinant human thyrotropin.