Multiple Lung Metastases of Papillary Thyroid Carcinoma Detected by Detailed Pathological Examination: A Case Series

Papillary thyroid carcinoma (PTC) is the most common histological type of malignant thyroid tumor, and the lungs are one of the most frequent sites of distant metastasis. Although the progression of the disease remains slow even after the appearance of pulmonary metastases, and there are reports of long-term survival cases, no clear criteria have been established for performing aggressive biopsies of metastatic lesions. The subject was a 79-year-old male who was detected to have left cervical lymphadenopathy of unknown origin six years back. After further examination, cervical lymph node metastasis of PTC was suspected. Five years ago, the patient underwent total thyroidectomy and left cervical lymph node dissection. Two years ago, a nodule was observed in the right upper lobe of the lung, but it was managed with observation. A chest computed tomography scan revealed an irregular nodule measuring 15×14 mm in the S1 segment of the right upper lobe. Under suspicion of primary lung cancer, it was decided to perform intraoperative rapid diagnosis, and if malignant, a right upper lobectomy with mediastinal lymph node dissection would be carried out. Intraoperative rapid diagnosis confirmed malignancy, and a right upper lobectomy and mediastinal lymph node dissection were performed. Histopathological examination revealed findings of papillary adenocarcinoma, leading to a diagnosis of secondary lung cancer (pT1cN0cM0, pStage IA3). In addition, findings suggestive of multiple metastases from PTC were also observed. Similarly, no adjuvant therapy was administered for the PTC lung metastases, and a policy of careful observation was adopted. This case is a valuable report of pulmonary metastasis from PTC discovered through detailed histopathological examination of the resected lung. Furthermore, performing aggressive surgical biopsy and detailed histopathological examination to establish a diagnosis is worth considering from the perspective of personalized medical care for each patient.