Rare ectopic thyroid tissue as multiple bilateral pulmonary nodules: a case report and literature review

The prevalence of ectopic thyroid tissue is 1 in every 100,000 to 300,000 persons in the general population, and ectopic thyroid tissue in the bilateral lung lobes is even rarer. Due to its rarity, there is no definitive or standard guidance on the diagnosis and treatment of ectopic thyroid tissue presenting as multiple bilateral pulmonary nodules.

A 56-year-old woman presented with multiple bilateral pulmonary nodules, and the patient had a history of hyperthyroidism but had no symptoms of ectopic thyroid tissue. Computed tomography (CT) demonstrated multiple solid nodules in both lungs, and the largest nodule (sized 15 × 14 mm) was located in segment 5 of the upper left lung. The initial diagnosis based on imaging was metastatic malignancies. Positron emission tomography-computed tomography (PET-CT) showed multiple bilateral intrapulmonary nodules that had slightly increased metabolism (SUVmax 1.7). The largest pulmonary nodule and another nodule in the left lung were resected by video-assisted thoracoscopy surgery (VATS). The pathological and immunohistochemical (IHC) examinations confirmed a diagnosis of ectopic thyroid tissue. No postoperative adjuvant therapy was given, and the patient was discharged 3 days after the operation and had regular follow-up examinations.

The diagnosis of ectopic thyroid tissue in the bilateral lung lobes is extremely difficult and should be considered carefully. PET-CT and surgical resection of intrapulmonary nodules are alternatives for clinicians in diagnosing ectopic thyroid tissue. Regular postoperative follow-up is needed.