RESUMO
Primary cardiac angiosarcoma is an exceedingly rare high-grade malignancy of the heart originating from endothelial cells, with a predilection for the right atrium in male. Clinical diagnosis is extremely challenging because of the nonspecific symptoms and radiological findings. Although almost always presenting with massive recurrent pericardial effusions, cardiac angiosarcoma diagnosed based on pericardial fluid has rarely been reported, either due to the paucity of malignant cells or misdiagnosis due to low familiarity/suspicion and lack of proper workup. Unfortunately, patients with this disease often receive definitive diagnosis post-mortem. We report a case of primary cardiac angiosarcoma initially diagnosed on pericardial fluid. The cytomorphology and immunophenotype of angiosarcoma in fluid, as well as the challenges and practical recommendations in using pericardial fluid cytology for early diagnosis of this deadly disease are discussed.