A 58-year-old lady, with a Hickman line in situ for chemotherapy for invasive ductal breast carcinoma, presented with fever. Blood cultures grew coagulase negative staphylococci. Transoesophageal echocardiography revealed a mass in the right atrium in the region of the Eustachian apparatus. The Hickman line was removed and the patient was treated for right-sided endocarditis. However, the mass persisted after prolonged intravenous antibiotics and a decision was made to remove it surgically. Histology revealed organised thrombus. The differential investigation of a right atrial mass in this position is discussed.