Abstract Introduction Pulmonary nodules almost always raise concern for malignancy, but sometimes appearances are deceiving. Ectopic thyroid tissue (ETT) in the lung is extraordinarily rare, with fewer than ten cases reported, yet it can look just like primary lung cancer or metastatic thyroid disease. Recognizing this entity is crucial to guide evaluation and management. Case Description An 81-year-old woman with atrial fibrillation, hypothyroidism, chronic anemia, and stage IB endometrioid carcinoma was referred for evaluation of right lower lobe pulmonary nodules and pleural effusions. She had previously undergone left thyroid lobectomy in May 2022 for a massive substernal goiter causing tracheal deviation and nighttime choking. Preoperative imaging showed a 5.9 × 1.9 cm left thyroid cystic nodule and a 2.2 × 1.0 × 2.0 cm mixed cystic-solid right thyroid nodule with macro-calcifications. One month postoperatively, she developed dyspnea. CT pulmonary angiography revealed large left and small right pleural effusions, left lower lobe compressive atelectasis, bilateral ground-glass opacities, and right lower lobe nodules measuring 13 mm and 6 mm, also visible on prior scans.Given her thyroid and oncologic history, metastases were suspected. Biopsy of the dominant nodule revealed benign thyroid follicles without atypia or mitoses. Ultrasound of the remaining right thyroid lobe showed a 1.5-cm nodule with benign cytology (Bethesda II). Prior thyroidectomy pathology confirmed multi-nodular hyperplasia without carcinoma. Multidisciplinary review concluded that the pulmonary nodules represented intrapulmonary ectopic thyroid tissue. Follow-up imaging showed the nodules remained stable. Discussion Intrapulmonary ETT is extremely rare and can closely mimic malignancy. Both benign and malignant thyroid tissue express TTF-1 and thyroglobulin, so histopathologic correlation with clinical and radiologic findings is essential. Awareness of prior thyroid surgery can provide context but does not prevent diagnostic uncertainty. Recognizing this entity is critical for accurate pulmonary evaluation and clinical decision-making. Learning Point Though rare, ectopic thyroid tissue should be considered in patients with a history of thyroid disease. Integrating imaging, pathology, and clinical context is key to an accurate diagnosis in pulmonary and critical care practice. Disclosure AI assistance was used for drafting and language refinement. All case content and interpretations were written and confirmed by the authors. This abstract is funded by: None
Batra et al. (Fri,) studied this question.