While the basic anatomy of the larynx already has been described in the section on early larynx cancer, this section will highlight the critical points relevant to treating patients with advanced cancers of the larynx. The majority of larynx cancers are found in the glottic region (56%) followed by the supraglottic region (41%), while tumors of the subglottic region are relatively infrequent (1 to 2%) (Figure 8-1).215 It is important to realize that tumors in these different regions of the larynx have different clinical behaviors. Supraglottic tumors, for example, have a much higher rate of occult and bilateral metastasis than glottic primaries.1016 The regional lymph nodes of the neck in patients with advanced stage supraglot-tic tumors and clinically negative necks must therefore be addressed in treatment planning.
The connective tissue barriers which lie between the mucosa and cartilaginous skeleton of the larynx, namely the conus elasticus and quadrangular membrane, are critical to the understanding of patterns of spread and clinical behavior of advanced cancers of the larynx (Figure 8-2). These membranes provide a barrier to the spread of cancer but are often breached
Figure 8-1. Site distribution of larynx cancers.
by advanced tumors (Figure 8-3).17 Once a tumor has broken through these boundaries, it can spread into the soft tissues of the neck as well as vertically within the larynx.
Two regions that are deep to the quadrangular membrane and conus elasticus are the preepiglottic and paraglottic space. Advanced tumors often enter these spaces when they transgress these connective tissue barriers within the larynx and thus enter a compartment where further spread is less hindered. The preepiglottic space is bounded by the thyrohyoid membrane anteriorly, the valleculae superiorly, the epiglottis posteriorly and the hyoid inferiorly. This space is commonly involved by local spread of supraglottic tumors. Once this space is involved, a supraglottic tumor is staged as a T3.18 Tumors involving this area can then spread into the soft tissues of the neck via the foramen in the thyrohyoid membrane or inferiorly via the paraglottic space. In some patients, however, a connective tissue barrier separates the preepiglottic and paraglottic space.19
The paraglottic space is the compartment which is bounded by the thyroid lamina laterally, the conus elasticus medially-inferiorly and the quadrangular membrane and preepiglottic space medi-ally-superiorly. Loose connective tissue and adipose tissue lying between thyroid lamina and the connective tissue membranes of the larynx occupy this space. This area is most commonly involved by advanced glottic tumors. Once this compartment is entered, tumors can spread relatively freely in a superior and inferior direction, as well as outside the confines of the larynx via the cricothyroid membrane or the preepiglottic space. Involvement of this space frequently results in decreased vocal fold movement.
Cancers of the larynx can be classified as advanced (stage III or IV) either by virtue of an advanced primary tumor or by the presence of regional lymph node metastasis. When regional lymph node metastases are present they are described by their location, number and size. The location of the lymph nodes is described by levels in the neck as illustrated in the chapter on neck metastasis. Levels II, III and IV are at highest risk for lymph node metastasis from cancers in the larynx.
Epiglottis Hyoid bone
Epiglottis Hyoid bone
Cricoid B cartilage
Figure 8-2. A, Sagittal section of larynx demonstrating the preepiglottic and B, coronal section of larynx demonstrating the paraglottic space.
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