Anatomical routes for cancer invasion of laryngeal cartilages.

The larynx is separated into compartments bounded by connective tissue membranes and cartilages. The membranes and cartilages affect the localization and spread of cancer for a while, but invasion eventually occurs. Histological study of the cartilages in the earliest stages of invasion shows cancer cells growing between the collagen bundles where the connective tissue membranes attach to the cartilages. At these points, the collagen bundles pass obliquely through the perichondrium to anchor into the cartilage and bone like Sharpey's fibers. As the cancer cells multiply, they separate the collagen bundles, forming linear passageways through the perichondrum. This appears to be the mechanism for cartilage invasion. Thus the sites of attachment of the strongest membranes are also the most frequent sites of invasion, i.e., the anterior commissure tendon and the cricothyroid membrane.