C43-30 A Tale of Two Goiters: Massive Cervical and Primary Mediastinal Goiters Causing Dyspnea

Abstract Introduction Primary mediastinal goiters are exceptionally rare, representing roughly 1% of all substernal goiters. They are characterized by complete anatomic separation from the cervical thyroid, a blood supply arising from mediastinal vessels, and the absence of prior thyroid surgery or malignancy. Unlike secondary substernal goiters that descend from the neck, primary mediastinal goiters originate within the mediastinum, most commonly in the anterior compartment. Although often hormonally inactive, they can produce compressive symptoms from gradual expansion and mass effect on intrathoracic structures. Case Presentation A 41-year-old woman with hypertension and class III obesity presented with progressive dyspnea, nausea, vomiting, and abdominal discomfort. CT abdomen performed incidentally revealed a large anterior mediastinal mass. Dedicated thoracic CT confirmed a well-encapsulated lesion extending to the inferior sternum, displacing mediastinal structures. Thyroid function tests were within normal limits (TSH 0.951 µIU/mL, T4 0.86 ng/dL, T3 3.06 pg/mL). Ultrasound demonstrated an independent multinodular cervical goiter, while radioiodine uptake scan showed normal thyroid activity but no radiotracer accumulation in the mediastinal mass, consistent with a non-functioning ectopic thyroid.Given progressive respiratory symptoms and mechanical compression, the patient underwent urgent resection requiring a combined cervical and median sternotomy approach. Resection and mobilization of the masses extended from the inferior aspect of the cardiophrenic angles to the superior aspect of the thyroid cartilage. Pathology revealed a 134 g multinodular thyroid and a 583 g mediastinal colloid goiter measuring 16.5 × 12.2 × 5.5 cm, both benign. Discussion Primary mediastinal goiters are thought to arise from aberrant embryologic migration of thyroid tissue or ectopic thyroid rests within the thymus. Their slow growth and hormonally inactive nature often delay diagnosis until compressive symptoms manifest or imaging detects an incidental mass. Pulmonologists and internists should consider this diagnosis in patients with unexplained dyspnea or mediastinal widening. Endocrinologic assessment, including thyroid function testing and radioiodine scanning, is essential to differentiate these from metastatic, thymic, or lymphoid lesions. In this case, the absence of radiotracer uptake and complete anatomic separation from the cervical gland fulfilled diagnostic criteria for a primary mediastinal goiter. Conclusion This case represents a rare coexistence of a massive primary mediastinal goiter and cervical multinodular goiter in an otherwise euthyroid patient. Recognition of this entity is essential, as early diagnosis allows for appropriate management before the development of severe compressive sequelae. This abstract is funded by: None