Case Report: Cardiac angiosarcoma with rib pain as the first symptom.

Primary cardiac angiosarcoma (PCAS) is a rare, highly aggressive malignancy characterized by a dismal prognosis. We present a case of a 34-year-old woman with no history of trauma who initially presented with persistent rib pain misdiagnosed as costochondritis. Comprehensive evaluation revealed multiple osteolytic bone metastases originating from a right atrial PCAS, accompanied by circumferential pericardial effusion. Despite initiation of palliative chemotherapy and radiotherapy, the patient succumbed to progressive disease five months after diagnosis. This case underscores three critical clinical considerations: (1) metastatic bone involvement may manifest solely as localized, refractory pain; (2) isolated pain without overt cardiac symptoms poses significant diagnostic challenges and risks delayed recognition; and (3) unexplained bone pain-particularly when concurrent with pericardial effusion-warrants prompt multimodal imaging and interdisciplinary evaluation involving oncology, cardiology, and pain medicine. By detailing the clinical, radiological, and histopathological findings, we aim to raise awareness among pain specialists and oncologists of this rare yet life-threatening cardiac malignancy and to advocate earlier diagnostic suspicion in atypical pain presentations.