63: Subglottic Resection of the Airway

Introduction

The use of cricotracheal resection in the treatment of cancer is rare owing to the rarity of cancers of the subglottis and their lack of confinement to the larynx. Of the three subsites of the larynx, the subglottis is the origin of squamous cell carcinoma (by far the most common cause of laryngeal cancer), in only 1% to 3% of patients.¹ Cricotracheal resection for the treatment of subglottic stenosis is much more common, and the surgical techniques used for treating subglottic stenosis can be applied to surgical resection of the rare neoplasm that remains confined to the subglottis.

The glottis is defined by the American Joint Committee on Cancer as the superior and inferior surfaces of the true vocal cords occupying a horizontal plane 1 cm in thickness extending inferiorly from the lateral margin of the ventricle, including the anterior and posterior commissures. The subglottis is defined as that region which extends from the lower border of the glottis to the lower margin of the cricoid cartilage.² On the basis of histologic sectioning of whole larynges, Kirschner³ was able to demonstrate that the conus elasticus represents the definitive anatomic boundary between the glottis and the subglottis. Tumors above the plane of the conus elasticus tend to behave as glottic tumors and remain within the confines of the larynx, whereas those below the conus spread more easily beyond the borders of the larynx and metastasize more commonly to the prelaryngeal, paratracheal, and mediastinal lymph nodes.^1,4 The epithelial lining also can be used to differentiate the glottis (lined by keratinizing squamous cells) from the subglottis (lined by ciliated respiratory epithelium).

Oncologic Principles

Although squamous cell carcinoma arises in the subglottis in only 1% to 3% of all laryngeal cancers, the subglottis is involved by contiguous spread of tumors of glottic origin in 11% to 33% of patients. These more common tumors are not amenable to cricotracheal resection.⁵ Early primary subglottic carcinomas are asymptomatic. Patients generally present with stage T3 or T4 tumors (Table 63-1), and airway obstruction is relatively common. These tumors usually exhibit circumferential growth, early cartilage invasion, and tumor growth beyond the borders of the larynx. Since glottic tumors with subglottic extension are not amenable to cricotracheal resection, and primary tumors of the subglottis of grade T2 or above are not contained within the subglottis, cricotracheal resection for squamous cell carcinoma is only possible for the rare T1 tumor. Otherwise, subglottic squamous cell carcinoma is treated with either radiation therapy or wide-field surgery, such as laryngectomy or laryngopharyngectomy. Tracheal tumors rarely extend superiorly to involve the subglottis. There is also strong evidence that subglottic squamous cell carcinomas should be treated aggressively, as there are poor outcomes published with advanced disease, and there is a propensity for nodal and distant metastasis.¹