Lung cancer is one of the most common worldwide. In Portugal it is the third most frequent in men and women. Unfortunately, it does not usually have a good prognosis because, most of the time, it is diagnosed in an advanced stage. It often has no symptoms, but some people may have a persistent cough (more than 3 weeks), lose weight or worsen shortness of breath, feel tired and/or chest pain. If you are concerned about any of these symptoms, especially if you are or have been a smoker, it is important to see a doctor.