Neurogenic tumors, Castleman disease, bronchogenic cysts, Bochdalek's hernia and mesenchymal tumors comprise a great proportion of masses localized in the posterior mediastinum. Though seen rarely, ectopic posterior mediastinal thyroid should also be included in diagnostic possibilities.
It is a benign condition and localized either retrotracheally or retroesophageally. In general, it occurs due to descent of a posterolaterally enlarging inferior pole of the thyroid gland. There may be a displacement in thyroid tissue due to their connection with these during the migration of large vessels in embryogenesis [2
Ectopic posterior mediastinal thyroid is often asymptomatic. Patients are usually euthyroid. However, symptoms related to the compression on adjacent organs, cough, dyspnea, wheezing, dysphagia, and obstruction of the superior vena cava may be seen. Occasionally, acute tracheal obstruction and severe respiratory failure may be observed [3
]. It is usually diagnosed incidentally during radiological procedures performed for other reasons, as in our case.
True malignant transformation in ectopic thyroid tissue is extremely rare [4
]. Nevertheless, these masses should be resected surgically due to the risks of malignant transformation, progressive enlargement, hemorrhage within the mass causing respiratory failure, and compression of neighbouring vital mediastinal organs. In the surgical approach, thoracotomy provides both surgical convenience and allows a complete resection with easy access and better visualization. This is a safe procedure with a very low mortality rate and an acceptable morbidity. Finally, complete resection is necessary for achieving a cure.
It usually gets anomalous blood supply from the major great vessels in thorax, especially from the aorta and may show adhesions to surrounding tissues. Therefore, these arterial structures must be ligated and dissection should be performed carefully not to injure the vital organs such as the trachea and the esophagus. In our case, right recurrent laryngeal nerve was adhered to the mass inferiorly and the mass was removed after the nerve was carefully separated from it. Blunt digital dissection without visual control may damage this nerve neighboring the mass and cause vocal cord paralysis postoperatively.