無症候性肺腺癌の初回診断時の心転移：症例報告

BACKGROUND Cardiac metastasis from lung cancer is rare and usually involves the pericardium. Myocardial or endocardial metastases are even less common and are often diagnosed postmortem or during late-stage disease when severe symptoms appear. Early detection in asymptomatic patients is challenging due to the heart's unique anatomy and the risks associated with myocardial biopsy. However, advances in imaging, particularly positron emission tomography-computed tomography (PET-CT) combined with magnetic resonance imaging (MRI), enable non-invasive diagnosis. Identifying such lesions before clinical symptoms emerge may help prolong survival. CASE REPORT A man in his 50s was diagnosed with right lower-lobe lung adenocarcinoma by needle biopsy and admitted for surgical evaluation. During preoperative staging, PET-CT and MRI revealed a lesion in the left ventricular myocardium, although the patient had no cardiac symptoms. Imaging suggested a metastatic focus. Due to the high risk of biopsy, pathological confirmation was deferred. The patient received systemic treatment combining chemotherapy and targeted therapy. After 2 treatment cycles, follow-up cardiac MRI showed that the lesion had decreased in size from 23×13×29 mm to 17×12×26 mm. CONCLUSIONS Myocardial metastasis from lung adenocarcinoma is extremely rare, especially in asymptomatic individuals. In such cases, PET-CT is essential for distant metastasis screening, and MRI is the most appropriate tool to evaluate cardiac lesions when biopsy is unsafe. Early detection enables timely systemic therapy and can prevent life-threatening events. Clinical efforts should focus on improved screening of high-risk patients and development of individualized treatment strategies.