Lung cancer. X-ray of the chest of a male patient with adenocarcinoma of the lung. A malignant (cancerous) tumour (white) is seen in the lower left lung (at right). The tube at top left is used to deliver chemotherapy drugs to the bloodstream. Adenocarcinomas arise from the lining (epithelium) of the lung. Lung cancers are usually caused by tobacco smoking, and are fatal unless caught early.