Implication of minimal extrathyroidal extension as a prognostic factor in papillary thyroid carcinoma

Extrathyroidal extension (ETE) of papillary thyroid carcinoma (PTC) is a risk factor for tumor recurrence. By TNM Classification (7th edition), differentiated thyroid carcinoma with ETE is designated T3 (minimal invasion), T4a (extended invasion), or T4b (more extensive unresectable invasion), according to the degree of tumor involvement. We subsequently focused our investigation on minimal ETE (MEE), analyzing the clinicopathologic characteristics, recurrence rate, and recurrence-free survival (RFS) in this setting.

A retrospective study was conducted, based on 332 patients undergoing thyroidectomy for PTC between January 2005 and December 2006.

The study population was stratified into two groups: PTC with MEE (103/332; 31.0%) and PTC without MEE (229/332; 69.0%). In patients with PTC, MEE correlated with gender, tumor size, multifocality, lymph node (LN) metastasis, underlying Hashimoto's thyroiditis, and the nature of the surgery. However, no significant intergroup differences were evident with respect to age, recurrence rate, and LN metastasis. In multivariate analysis, LN metastasis (odds ratio = 2.273; 95% confidence interval, 1.280-4.037) was recognized as an independent correlate of mETE (p = 0.005). However, recurrence-free survival did not differ significantly between the groups (p = 0.153), even when further stratified by the presence or absence of LN metastasis.

In patients with PTC, MEE does not impact RFS. Thus, appropriate surgical intervention and postoperative follow up are mandatory in PTC, regardless of its extent.