The patient with differentiated thyroid cancer involving the airway may present with classical symptoms and signs of airway neoplasm, namely, hemoptysis, wheezing, dyspnea on exertion, and, additionally, hoarseness.
More often, airway involvement produces no symptoms, since the tumor has not yet penetrated the mucous membrane or projected any distance into the lumen. A firm mass may be palpated, which is not freely movable over the trachea. Often, tracheal and laryngeal involvement are discovered at thyroidectomy.
In my opinion, in addition to the usual diagnostic approach to thyroid cancer (thyroid function studies, thyroid scan, and needle biopsy), flexible bronchoscopy is advisable for every such patient, despite the rarity of visible airway invasion. However, there is not yet a completely accurate method to distinguish close abutment of the tumor to the tracheal wall from actual early invasion. Linear x-ray studies of the trachea include filtered views and crisp tomography, which are of great use in determining the extent of gross involvement of the larynx and trachea, and also the relative portion of the airway that is not involved (Figure 8-4). Fluoroscopy of the larynx adds information about the function of the vocal cords to that obtained by direct laryngoscopy (Figure 8-5). The neck should be imaged using thin section computed tomography (CT) scans, which are most likely to identify involvement of the tracheal wall or intrusion into the lumen (Figure 8-6). CT scanning should include the chest, to search for pulmonary metastases. Magnetic resonance imaging (MRI) is also useful in defining these lesions. Barium swallow may define the bulk of tumor and suggest esophageal involvement. Preoperative studies that are appropriate for exenteration, which may be considered for massive invasive tumors, are described in Chapter 34, "Cervicomediastinal Exenteration and Mediastinal Tracheostomy."
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