A 58-year-old male who complained of chest oppression on effort was diagnosed as aortic regurgitation by echocardiography. The cardiac catheterization was showed moderate aortic regurgitation. He was referred to our hospital for aortic valve replacement. We considered preoperatively that the aortic regurgitation is due to infective endocarditis or aortitis syndrome. We have not noticed cardiac tumor at all until aortic valve replacement. Postoperative pathological diagnosis of the tumor was malignant lymphoma. The tumor had a characteristic architecture of a cardiac MICE (mesothelial/monocytic incidental cardiac excrescence). After the operation, additional chemotherapy using doxorubicin and cysplatin was performed. The patient has been doing well for 5 years after operation.