Ectopic papillary thyroid carcinoma mimicking distant metastatic tissue

We report a case of a 50-year-old woman presenting with a solid nodule in each lung. She was previously suspected of having lung cancer and distant pulmonary metastasis on the basis of imaging findings. Surgical pathology revealed that the left lung nodule was adenocarcinoma, but the contralateral nodule was papillary thyroid carcinoma (PTC). We subsequently performed total thyroidectomy, and the histological findings of the resected specimen showed no suspicious tumor tissue. Overall, the results led to a diagnosis of ectopic intrapulmonary PTC with synchronous lung adenocarcinoma. Ectopic intrapulmonary PTC is a rare but true phenomenon that may be easily mistaken for pulmonary metastasis in daily practice. It is important to improve the recognition of ectopic intrapulmonary thyroid tumors to avoid misdiagnosis.