Lung cancer is the most common malignancy worldwide, with more than 1 million cases diagnosed yearly. Lung cancer develops when normal processes of cell division and growth are disrupted, giving way to abnormal, uncontrollable growth. The cells grow into a mass, or tumor. Any abnormal growth in the body that directly invades surrounding tissues and organs, spreads to other parts of the body, or has the potential to grow back after being removed is called “malignant,” or cancerous.