Predictors of Thyroid Gland Invasion in Laryngeal Squamous Cell Carcinoma

Introduction: Laryngeal squamous cell carcinoma (SCC) can invade the thyroid gland leading to unnecessary thyroidectomies with subsequent hypothyroidism and hyperparathyroidism. Thus, clinicopathological variables should be defined in order to predict thyroid gland invasion preoperatively.   Materials and Methods: We performed a retrospective analysis of 1,465 patients with laryngeal SCC referred to our center between March 2009 and January 2016. Among these patients, 60 individuals underwent total laryngectomy and either thyroid lobectomy and isthmectomy or total thyroidectomy.   Results: Thyroid gland invasion was observed in 20% of samples. The following variables were associated with thyroid gland invasion: transglottic spread of the tumor (odds ratio [OR]: 2.04, 95% confidence interval [CI]: 1.15–5.81, P=0.004), thyroid cartilage involvement (OR: 1.53, 95% CI: 0.94–2.50, P=0.02), and anterior commissure involvement (OR: 5.75, 95% CI: 0.86–38.42, P=0.01). In addition, the largest dimension of the tumor was significantly associated with thyroid gland involvement (r=0.36, 95% CI 0.05–0.67, P=0.004). Multivariate linear regression analysis confirmed these findings.   Conclusion: The rate of thyroidectomies performed in cases of laryngeal SCC is much higher than the actual rate of thyroid gland invasion. Thus, preoperative evaluation to find transglottic spread of the tumor, thyroid cartilage, and anterior commissure involvement should be considered.