Abstract
A 67-year-old man underwent preoperative computed tomography (CT) owing to the presence of a thoracic aortic aneurysm. CT showed a ground-glass nodule in the left lower lobe of the lung. We performed video-assisted thoracoscopic surgery (VATS) wedge resection of the nodule. The pathological diagnosis was lepidic pattern-based lung adenocarcinoma, pT1miN0M0-IA1 (UICC 8th). Two years and five months later, he came to the hospital complaining of dyspnea, and a chest radiograph showed mass pleural effusion in the left lung field. We performed VATS pleural biopsy of the left lung base where the pleural thickening was observed. The pathological diagnosis was poorly differentiated adenocarcinoma.
Pathologically differentiating metastasis from metachronous lung adenocarcinoma was difficult; therefore, we performed examinations using a comprehensive cancer panel, which revealed an EGFR p.R521K mutation in both tumors. Further, somatic mutations were observed in approximately 90% of the cells in both tumors. These results facilitated a diagnosis of metastasis. The patient has been undergoing chemotherapy with cisplatin and pemetrexed.
