Lung cancer is a generally terminal form of cancer. Almost all lung cancers are carcinomas, but some are secondary tumors from metastasis of other tumors. Once rare, they become much more common as smoking increases in a population, and similarly fall in incidence when smoking rates are lower. However, they can also be caused by radon gas, asbestos, air pollution, and genetic causes.
Although fairly common in the population, a diagnosis is still a zebra because the symptoms in patients can be very different and non-specific. A medical history and thorough differential diagnosis are key to diagnosis, although most tumors will show up on radiological investigation.