Choriocarcinoma presenting with cystic lung metastasis mimicking diffuse cystic lung disease

Choriocarcinoma is a highly aggressive malignant germ cell tumour containing syncytiotrophoblasts that secrete beta-human chorionic gonadotropin, and it has a poor prognosis, with a dismal 5-year survival rate of <5%. It generally affects young individuals. Cystic lesions in the lung are uncommon in malignancies that can predispose patients to spontaneous pneumothorax. Multiple cystic lesions are less commonly seen in metastatic disease. Diffuse cystic lung diseases (DCLD) are a group of diseases characterised by cysts in the bilateral lung fields that are not necessarily evenly distributed. The differential diagnosis is limited and typically includes lymphangioleiomyomatosis and pulmonary Langerhans cell histiocytosis. Sometimes, metastatic malignancy can present as DCLD. Metastatic leiomyoma, endometrial stromal sarcoma and cellular fibrous histiocytic tumours have been reported as causes of lung cysts. We report a case of choriocarcinoma with cystic lung metastasis in a woman in her 30s.