The esophagus and trachea develop during the third week of gestation as the primitive foregut is divided by lateral septa into the ventral (tracheal) and dorsal (esophageal) buds [2
]. Bronchogenic cysts occur when the communication with the tracheobronchial tree is completely lost, although those in the mediastinum frequently remain attached. They may arise anywhere along the tracheoesophageal course, most commonly in the mediastinum or lungs. In very rare instances, such cysts may occur in the thyroid gland. This is likely secondary to budding that occurred during later stages of embryological development [3
]. Usually these cysts present during childhood as isolated extrapulmonary, paratracheal masses [4
]. Extrathoracic bronchogenic cysts have been reported in less than 10% of cases [5
]. Irrespective of their location, bronchogenic cysts are usually asymptomatic but may produce symptoms of stridor, pain, fever, cough, or dyspnea due to compression of neighboring structures or secondary infection. Most cases are detected during routine radiographic imaging that shows abnormal shadowing [5
The diagnosis of a bronchogenic cyst is made based on histopathologic features. The lining of these cysts is comprised of pseudostratified ciliated columnar epithelium. The wall may also have interspersed areas of smooth muscle, mucus-secreting goblet cells, cartilage, and dystrophic calcification [5
]. Not all of these features need to be present in order to make the diagnosis.
The differential diagnosis of cervical bronchogenic cysts includes thyroglossal duct cysts, parathyroid cysts, thyroid cysts, cervical thymic cysts, cystic hygromas, dermoid cysts, teratomas, and cystic neuromas [5
]. In our case, it was difficult to clinically distinguish a thyroid adenoma or cyst from a bronchogenic cyst. The diagnosis was confirmed by microscopic examination of the specimen showing many of the typical features of a bronchogenic cyst, as previously described.
In rare cases, bronchogenic cysts follow a malignant course [5
]. Therefore, surgical resection is recommended. Complete resection is ideal, but since most cysts are benign, radical resection should be avoided. In most cases, patients do well post-operatively.
In summary, our case highlights the possibility of a bronchogenic cyst in the differential diagnosis of a painful thyroid mass.