Aberrant Thyroid Tissue

Fig. 7.2. Oncocytic cyst of the ventricular cord. Cyst is lined with oncocytic epithelium a diffuse involvement as oncocytic cystadenomatosis is exceptional [230].

Histologically, the epithelium of an OC shows papillary proliferations or a different degree of folding of the cystic wall. The epithelium is typically double layered; the inner layer consists of columnar eosinophilic cells encircling the cystic lumina, while the outer layer is composed of small basal cells (Fig. 7.2). Complete en-doscopical surgical excision is the recommended treatment, if necessary by laryngofissure [216].

An outpouching of the dorsal hypopharyngeal wall above the upper oesophageal sphincter is known as Zenker's diverticulum (ZD). The condition is more often seen in northern Europe, especially the UK, than elsewhere in the world [42]. The site of origin is between the thyropharyngeal and the more horizontal part of the cricopharyngeal muscle. The aetiological factors of ZD occurrence have not been explained, but an incomplete sphincter opening with an increase in hypopharyngeal pressure during swallowing has to be considered [266]. The lesion, which usually occurs in elderly persons, is now widely accepted to be of ac

Thyroid tissue rarely appears in sites outside of its embryonic development. The subglottic area of the larynx and upper trachea are places where aberrant t hyroid tissue (ATT) may be found [36], especially between the lower border of the cricoid cartilage and the upper ring of the trachea. According to different reports, intraluminal thyroid tissue occurs anywhere between the glottis and the bifurcation of the trachea, as a broad-based, smooth, rounded mass protruding from the left subglottic posterolateral wall [305, 345]. It has been pointed out that two-thirds of patients are middle-aged women from regions of endemic goitre [22, 36]. Intralaryngotracheal thyroid is a rare lesion. Only about 125 cases were described up to 1998 [327]. Waggoner divided intralaryngotracheal thyroid tissue into "false" and "true" aberrant thyroids. The former is likely to arise in the pre- or neonatal period, when the thyroid gland could grow into incompletely formed laryngotracheal cartilages that remain in continuity with the thyroid gland. The latter, the "true aberrant thyroid", develops during the foetal period as an isolated, misplaced thyroid tissue, when the thyroid gland is encroached upon and divided by the later developed laryngeal and tracheal cartilages [327, 361, 372]. The most common symptom of intralaryngeal ATT is slowly progressive dyspnoea, but it may be also asymptomatic [278].

Histologically, the thyroid follicles are usually small, regular, with a well-formed colloid lying close to the se-romucinous glands in the laryngeal mucosa [238]. The overlying mucosa is commonly intact, and there may be some evidence of chronic irritation. The finding of thyroid tissue in the laryngotracheal wall raises the question as to whether or not it represents ectopic tissue appearing through a developmental defect or a well-differentiated carcinoma. The final decision must be based on an overall clinical evaluation and not only on histologi-cal findings [36, 327]. Management of ATT is often not clear-cut, but is proposed to be primarily surgical [327, 345, 372].

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