Diagnosis: Iatrogenic ectopic thyroid
In the third to fourth weeks of normal development, the thyroid gland forms as a midline diverticulum from the foramen cecum between the first and second branchial arches. It descends inferiorly anterior to the hyoid bone and eventually to the lower area of the neck. Specifically, it develops between the hypobranchial eminence, which is the precursor to the posterior third of the tongue, and the tuberculum impar, which forms the anterior two-thirds of the tongue. The median cluster of cells is a bilobed diverticulum, forming the bulk of the gland; it descends caudally during development and fuses with the lateral cluster of cells that are derived from the ultimobranchial bodies (fourth pharyngeal pouch). This lateral cluster of cells provides 30% of the thyroid parenchyma. The complete thyroid gland is a fusion of median and lateral anlages.1,2
Radiology Quiz Case 2: Diagnosis. JAMA Otolaryngol Head Neck Surg. 2013;139(2):190–191. doi:10.1001/jamaoto.2013.1287b
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