Primary Pulmonary Choriocarcinoma Presenting with Pulmonary Embolism and Hypomagnessemia-Induced Arrhythmia: A Rare and Diagnostically Challenging Case

Background: Choriocarcinoma is a germ cell tumour with highly malignant clinical behaviour. Its non-gestational, or primary subtype is associated with a poor prognosis and marked angioinvasiveness. Primary pulmonary choriocarcinoma (PPC) is exceedingly rare malignancy with no clinical guidelines developed for its treatment and the data on its symptomatology and optimal management remain limited. We report a 37-year-old woman who presented with sudden onset right-sided chest pain, dyspnoea, and cough. Computed tomography scan of the chest demonstrated a right-sided lung mass, and an initial percutaneous needle biopsy suggested a poorly differentiated lung carcinoma. She underwent right pneumonectomy, and postoperative histology of the resected mass confirmed pulmonary choriocarcinoma. While awaiting chemotherapy, she developed clinical features of pulmonary embolism and a malignant arrhythmia that markedly worsened her prognosis despite treatment. A dramatic clinical turnaround was experienced following intravenous magnesium sulphate correction of an incidentally detected hypomagnesemia. She commenced the etoposide, methotrexate, actinomycin D, cyclophosphamide and vincristine (EMA-CO) regimen with a suboptimal response, and was subsequently transitioned to bleomycin, etoposide and cisplatin (BEP), on which she demonstrated marked clinical improvement. This case illustrates the diagnostic difficulty inherent in the evaluation of patients with primary pulmonary choriocarcinoma thus emphasizing the need to consider this rare entity in cases of lung masses, the central role of surgical resection within a multidisciplinary treatment strategy, and the often under-recognized contribution of hypomagnesemia to cardiovascular instability in critically ill oncology patients.