Objectives: 1) Review the incidence of thyroid gland invasion by squamous cell laryngeal carcinoma reported in the literature. 2) Assess the association between thyroid gland invasion and anatomical characteristics of the laryngeal tumor.
Data sources: MEDLINE (1967-2007) and EMBASE (1980-2007). These databases were supplemented with 61 patients from McGill University who underwent total laryngectomy with hemi- or total thyroidectomy from 2001-2006.
Review methods: Systematic review for series of laryngeal carcinoma that commented on thyroid gland invasion according to tumor subsite and pathological characteristics. Total laryngectomy specimens for primary laryngeal squamous cell carcinoma with concomitant thyroid resection were included in the analysis.
Results: In total, eight series (n = 399) were included in the meta-analysis. Thyroid gland invasion was present in 33 laryngectomy specimens (8%); the principal method of invasion of the gland was by direct extralaryngeal extension. Subglottic extension > 10 mm (OR 7.22 [2.05 to 25.46]; P = 0.002), transglottic tumors (OR 3.23 [1.16 to 9.00]; P = 0.025), and subglottic subsite (OR 5.66 [1.34 to 23.87]; P = 0.018) were all significantly associated with thyroid gland invasion. Cartilaginous invasion by tumor was not a significant predictor of thyroid gland invasion (P > 0.05).
Conclusions: Thyroid gland invasion is not a general feature of squamous cell laryngeal carcinoma. When present, it is strongly associated with anteroinferior spread of advanced laryngeal tumors. Thyroidectomy may only be required during total laryngectomy for transglottic tumors, subglottic tumors, and tumors with subglottic extension >10 mm.