Wan Muhamad Hatta, Syarifah SyafiqahMirza, Abdur RahmanSunni, NadiaBashir, Ahmed2025-03-252025-03-252025-01-18Wan Muhamad Hatta SS, Mirza AR, Sunni N, Bashir A. Heart-breaking tumours: a case series of malignant pericardial effusion. Eur Heart J Case Rep. 2025 Jan 18;9(3):ytaf009. doi: 10.1093/ehjcr/ytaf009. PMID: 40046975; PMCID: PMC11879449.2514-211910.1093/ehjcr/ytaf00940046975http://hdl.handle.net/20.500.14200/7327Background: Malignant pericardial effusions are often linked to metastases from solid tumours, such as those in the lung or breast, or haematological diseases. Primary cardiac tumours are rare, occurring in only 0.02% of cases, with pericardial tumours comprising 6.7%-12.8% of all primary cardiac tumours. Case summary: In Case 1, a 49-year-old Black African male presented with chest pain and breathlessness after a COVID-19 vaccine. Initially treated for pericarditis, he returned with worsening symptoms. Echocardiography revealed pericardial effusion and cardiac tamponade. Imaging confirmed a right atrial mass diagnosed as malignant biphasic mesothelioma. He died 4 months after diagnosis. In Case 2, a 43-year-old Caucasian male developed breathlessness and fever post-COVID-19 vaccine. Imaging identified a large posterior pericardial mass, later diagnosed as synovial sarcoma. Chemotherapy yielded minor tumour reduction, but he succumbed to his illness, spending his final days in a hospice. Discussion: Initial clinical signs are critical in determining the origin of pericardial effusion. Malignancy should be suspected in cases with cardiac tamponade, unexplained haemorrhagic pericardial fluid, or recurrent symptoms. Negative cytology warrants further investigation with advanced imaging or biopsy to improve diagnostic sensitivity. Diagnosing rare tumours involves multiple imaging modalities, fluid analysis, biopsies, and an interdisciplinary approach, with pathological analysis being the gold standard. Treatment remains challenging due to the rapid progression of these tumours, with surgery often not feasible. A multi-pronged diagnostic approach is crucial, and clinicians must maintain suspicion for malignancy in persistent pericardial effusion cases, even in the context of other potential confounding factors.en© The Author(s) 2025. Published by Oxford University Press on behalf of the European Society of Cardiology.CardiologyArticle