A 50-year-old woman presents with complaints of generalized fatigue and shortness of breath which has worsened over the past few days. On examination, fine crackles are heard on auscultation and echocardiogram shows an enlarged left atrium due to a large mass in the left atrium along with calcification of the mitral valve. Before open heart surgery can be performed, the patient dies due to an ischemic brain stroke. The heart at autopsy is shown in the image.

Which of the following is the most likely diagnosis?