Pericardial malignant infiltration as the cause of sudden death of a patient with metastatic urothelial carcinoma treated with atezolizumab.

Cardiovascular toxicity of atezolizumab was considered within differential diagnoses, however histopathological examination revealed progression of malignancy in the pericardium as the cause of the sudden death. This is the first published case report of a patient treated with second-line atezolizumab in whom the rare disease progression of pericardial infiltration was confirmed. Despite its rarity, the clinicians should always consider the possibility of pericardial metastases.