Male patients with papillary thyroid cancer have a higher risk of extranodal extension.

[BACKGROUND] There is a sex disparity in papillary thyroid cancer (PTC). Male sex is associated with a higher likelihood of advanced stage disease. This study aimed to examine the significance of sex for extranodal extension (ENE) in PTC.

[METHODS] We reviewed the data of PTC patients who had undergone initial surgical resection from July 2012 to December 2014 (N = 1531). The effects of sex and other clinicopathological factors on ENE were investigated.

[RESULTS] Of 1531 patients identified, 377 (24.6%) were male, 816 (53.3%) had positive nodes, and 256 (16.7%) had ENE. Compared with female patients, male patients had a higher risk of ENE (P < 0.001). Multivariable analysis of clinicopathological factors revealed that male sex (odds ratio [OR], 1.98; 95% confidence interval [CI], 1.37-2.87; P < 0.001), age older than 60 years (OR, 1.93; 95% CI, 1.08-3.35; P = 0.023), extrathyroidal extension (OR, 3.52; 95% CI, 2.42-5.14; P < 0.001), bilateral multifocality (OR, 2.18; 95% CI, 1.53-3.13; P < 0.001), and more positive nodes were significantly associated with increased risk of ENE. Patients with 6-10 positive nodes were 16.45-fold higher to have ENE than patients with 5 positive nodes or less (95% CI, 11.07-24.68; P < 0.001).

[CONCLUSION] Male PTC patients had a higher risk of ENE than female. Sex was an independent predictor of ENE. The underlying mechanism needs to be investigated further.