Anatomic Foramina in the Thyroid Cartilage: Incidence and Implications for the Spread of Laryngeal Cancer

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Abstract
Anatomic openings in the posterosuperior portion of the thyroid lamina of the larynx were first described in the 19th century. In the present study of 121 coronally sectioned larynges, such openings were found in 47 (39%), appearing bilaterally in 15 and unilaterally in 32. In a separate study of 69 cadaver larynges, the openings were found in 39 (57%), appearing bilaterally in 16 and unilaterally in 23. In 51 laryngectomy specimens removed for squamous cell cancer and showing foramina, tumor was not observed to invade or traverse the foramen in a single case, even in those specimens with tumor overlying the foramen and displaying framework invasion at other sites. Invasion by cancer through the foramen appears to be prevented by a layer of fibroelastic tissue overlying the medial surface of the foramen, parallel to the inner surface of the thyroid lamina. This layer of fibroelastic tissue may represent perichondrium.