Substernal thyroid masses.

A thyroid mass, most often a non toxic colloid goiter or occasionally an adenoma, is not an unusual finding below the level of the thoracic inlet.1 In 1992 Creswell and Wells estimated that these tumors comprise 5.8% of all mediastinal lesions.1 There is no standard definition for thyroid glands extending below the thoracic inlet, but such masses descend from their original cervical location for more than 2 or 3 cm below the thoracic inlet, and are not truly primary tumors of the mediastinum. They preserve the connection between the thoracic and cervical portion and receive their blood supply from the neck.2,3 In 1940, the seminal report of Wakeley and Mulvany divided intrathoracic thyroid masses into 3 types; (1)”Small substernal extension” of a mainly cervical mass, (2) “Partial” intrathoracic, in which the major portion of the mass is situated within the thorax, and (3)”Complete” in which all of the mass lies within the thoracic cavity.1 It has been found that 80% of the substernal thyroid masses are of small extension type, 15% are of the partial type and 2-4% is of the complete type. These masses extend into the visceral compartment of the mediastinum and even the anterior substernal extension remains in the same compartment, being confined anteriorly by the pre-tracheal fascia.1 An intrathoracic goiter on the right side which is anterior or anterolateral to the trachea originally enters the mediastinum via the visceral compartment, but once within the thorax, the lower aspect of the mass may pass in front of the ascending arch of the aorta into the anterior mediastinum. Substernal enlargement of a goiter can cause compression of several mediastinal structures including the trachea, esophagus and superior vena cava, and these indicates urgent resection of the mass.4,5 These tumors either partial or complete will require surgical excision, usually through the cervical incision.4-8 In this study we review our experience and surgical approach for thyroid masses extending to a variable extent into the mediastinum and compressing the trachea. This study is a retrospective one. This is a review of medical charts and radiological images of 16 patients with substernal extension of thyroid gland that were operated upon during the period of 2006 to 2009 at King Fahad University Hospital. Twelve patients (75%) were females and only four patients (25%) were males. The mean age was 45 years. The prominent preoperative presentations were a palpable neck mass of variable size (15=93.75%), dyspnea (14=87.5%), and dysphagia (4=25%). Thyrotoxic manifestations were only present in 2 cases (12.5%), while all the other cases (14=87.5%) were euthyroid. Routine blood investigations, thyroid function tests and thyroid antibodies were done to all patients. Chest X-ray (CXR), Computed Tomography (CT) neck and upper chest were done to all patients and showed variable degrees of tracheal compression. (Figs. 1,2) Indirect laryngoscopy was also done as a preoperative routine to all patients. Tracheal compression was clearly diagnosed radiologically, but in 4 cases (25%), bronchoscopic evaluation of the airways was needed to exclude infiltrations and to assess the condition of the trachea. Esophagoscopy was required in only 2(12.5%) patients presented with severe dysphagia to exclude esophageal lesions. Preoperative Fine Needle Aspiration Cytology (FNAC) was done in 5(31%) patients only when we suspected malignancy, while the other 11 patients were planned for thyroidectomy without FNAC.