Lung cancer cells, coloured scanning electron micrograph (SEM). Lung cancer occurs when abnormal cells divide in a chaotic and uncontrolled manner resulting in the formation of a tumour in the lungs. It is more commonly found in older people and one of the most common factors associated with getting lung cancer is smoking. Other causes or risks associated with getting lung cancer are exposure to chemicals or pollutants or a family history of lung cancer. There are a number of treatments available for lung cancer depending on what type of lung cancer it is and the stage it is at. These may include surgery, chemotherapy and radiotherapy, immunotherapy and targeted cancer drugs. Magnification: x2400 when printed at 10cm wide.