Primary Extragonadal Choriocarcinoma Presenting with Pneumothorax in an Elderly Male Patient: A Case Report.

Introduction: Non-gestational choriocarcinoma is an extremely rare and highly aggressive trophoblastic malignancy in male patients. It frequently presents with multiorgan metastases and poor prognosis. Spontaneous pneumothorax associated with metastatic pulmonary tumors is uncommon and may indicate rapid tumor progression. Here, we report a rare case of primary extragonadal choriocarcinoma presenting with pneumothorax in an elderly male patient. Case Presentation: An 80-year-old man presented with cough and dyspnea. Chest computed tomography revealed right pneumothorax, more than 30 bilateral pulmonary nodules, mediastinal lymphadenopathy, and hepatic lesions. Persistent air leakage required thoracoscopic surgery. Histopathological examination of the resected lung specimen demonstrated hemorrhagic and necrotic nodules with biphasic trophoblastic morphology. Immunohistochemistry was positive for GATA binding protein 3, human chorionic gonadotropin, and CK7, leading to the diagnosis of choriocarcinoma. The serum human chorionic gonadotropin level was markedly elevated at 17,000 mIU/mL. Positron emission tomography/computed tomography revealed no abnormalities in the testes, and the tumor was considered most consistent with primary extragonadal choriocarcinoma. Despite temporary postoperative improvement, the disease progressed rapidly and the patient died on hospitalization day 24. Conclusion: This rare case highlights that choriocarcinoma should be considered in the differential diagnosis of pneumothorax accompanied by multiple pulmonary nodules, even in elderly male patients. Pneumothorax occurring before treatment may reflect highly aggressive tumor behavior, emphasizing the importance of early pathological diagnosis and prompt clinical intervention.