Lung malignancy invading the left atrium is rarely seen. We present a patient with a fast growing symptomatic lung mass. Electrocardiogram showed persistent coving ST elevation with no biomarker change. Transthoracic echocardiography showed a large left atrial mass attached to the free walls and extended into its appendage. An apparent continuity with a large lung mass compressing left ventricular lateral wall was observed which was better evident in computed tomography of the chest.