Coexisting benign and malignant tumours: a cardiac angiosarcoma case report.

Background: Primary cardiac tumours are rare. When patients present with both cardiac and extracardiac masses, clinicians may opt to biopsy accessible peripheral lesions to guide diagnosis, but benign findings can provide false reassurance. This case demonstrates the diagnostic pitfall of this approach when multiple concurrent pathologies coexist. Case summary: A 79-year-old male presented with progressive peripheral oedema, dyspnoea, and chest pain. Echocardiography revealed a 6.5 cm mobile intracardiac mass originating from the right atrial appendage. Pericardiocentesis drained 1100 cc of haemorrhagic fluid with negative cytology. PET-CT showed FDG uptake in the cardiac mass as well as multiple extracardiac lesions. Biopsy of a left upper arm lesion revealed a benign peripheral nerve sheath tumour. Photon-counting CT deemed angiosarcoma less likely due to limited contrast enhancement. These findings combined initially lowered suspicion for cardiac malignancy. The patient underwent surgical resection via median sternotomy. Histopathology revealed a high-grade angiosarcoma with positive resection margins (CD31+, CD34+, ETS-Related Gene [ERG]+, Ki-67 40%-60%). The postoperative course was uncomplicated, and the patient was transferred to the referring hospital on postoperative day four. Discussion: This case demonstrates that benign pathology from peripheral lesions should not eliminate suspicion for cardiac malignancy when clinical features such as haemorrhagic pericardial effusion, right heart failure, and thromboembolic complications are present. Multiple concurrent pathologies can coexist, underlining the limitations of extrapolating peripheral biopsy results to cardiac masses.