Carcinoma of the anterior commissure of the larynx: I. Embryological and anatomic considerations.

In this study we attempt to define the organization of the anterior region of the adult larynx, on the basis of its development. For this purpose, we have studied the development of the anterior commissure region on serial sections of human larynges from embryos, fetuses, and adults. Our findings indicate that all the structures of this region derive from a single median mesenchymal band, first evident at 7 to 8 weeks of gestation, between the lateral laminae of the thyroid cartilage. This band of mesenchyme gives rise to all the structures along the midline of the thyroid cartilage and immediately beyond, including the intermediate lamina of the thyroid cartilage, the median process, and the connective tissue that connects the latter with the conoid ligament. We provide, for the first time, evidence that Broyles' ligament (commissural tendon) derives from the dorsal part of the median process and becomes intimately connected with the surrounding structures, including the insertion fibers of the vocal muscles, from early in development. On the basis of this finding we identify an independent anterior commissure region in the adult larynx, which comprises the intermediate lamina, Broyles' ligament, the connective tissue between the Broyles' and conoid ligaments, and the insertion fibers of the vocal muscles. The interpretation of all these structures as a unified region can explain the peculiar progression pathways and evolution of commissural and cordo-commissural tumors.