Lung cancer. Coloured magnetic resonance imaging (MRI) scan of a sagittal (side) section through a human lung, showing a malignant tumour (yellow) in the lung apex. The apex is the top part of the lung, which extends into the neck. Cancer cells divide rapidly and chaotically. They may clump to form tumours (as seen here), which invade and destroy surrounding tissues. Lung cancer causes a cough, chest pain, shortness of breath and weight loss. If the cancer has not spread to other tissues (metastasis) then the tumour may be removed surgically. Other treatments include chemotherapy (anti-cancer drugs) and radiotherapy.