A 75-year-old male patient had his first acute ischemic stroke attack two years ago. After the Holter monitoring, the patient was diagnosed with paroxysmal atrial fibrillation. Simultaneously, transthoracic echocardiographic examination (TTE) was performed, which provided mitral annular calcification without any thrombus or tumor formation within the intra-cardiac cavity. Vitamin K antagonist and warfarin were offered; however, the patient refused to take them. Therefore, he was prescribed a new oral anticoagulant, i.e., apixaban at 5 mg twice a day. The patient was admitted to our neurology department due to the second ischemic stroke attack one week ago. Contrast computed tomography angiography showed non-significant atherosclerotic plaques in the right and left carotid arteries. Therefore, the patient was consulted by our department to exclude any sources of cardioembolism. TTE showed a hyper-echogenic mass located on the posterolateral mitral valve (Figure 1A). The 3D transesophageal echocardiography examination showed a hyper-echogenic mass with a diameter of 11x15 mm that was located on the left-ventricular side of the mitral valve (Figure 1B and 1C). Cardiac magnetic resonance imaging was performed to aid the diagnosis. It revealed a mass that was compatible with a cardiac calcified amorphous tumor (CAT) (Figure 1D). The patient underwent cardiac valve surgery, including tumor resection due to thromboembolism (Figure 1E and 1F). Pathological examination confirmed the diagnosis of cardiac CAT.

CAT is an extremely rare non-neoplastic cardiac tumor, which is pathologically characterized by calcification and amorphous fibrinous material (1). CAT is usually asymptomatic, and it is incidentally detected with cardiac imaging (2). However, as in our case, CAT should be considered in the differential diagnosis of patients who present with acute ischemic stroke due to thromboembolism. Additionally, our case demonstrates that when this tumor is present, apixaban treatment may be ineffective for preventing thromboembolism in such patients.