Two-dimensional transthoracic echocardiography is commonly performed to detect a possible cardiac source of systemic embolism and it has been the mainstay of detection and diagnosis of cardiac masses. The transesophageal approach has enhanced the ability to detect cardiac sources of embolism by allowing a better visualization of posterior cardiac structures such as the left atrium with left atrial appendage, pulmonary veins and thoracic aorta and by providing higher resolution images to improve assessment of the presence and extent of cardiac masses. In this case report, echocardiography, using both transthoracic and transesophageal approach, allowed to detect a neoplastic mass arising from the upper left pulmonary vein in a patient presented with a transient ischemic attack. Further investigations showed a malignancy involving the lung. To our knowledge, this is the first reported case in which a cerebral embolic episode represents the clinical onset of a lung cancer, pointing out the importance of echocardiography in all cases of undetermined cerebral ischemic attack.