Final answer:
Metastatic lung cancer is cancer that originates in the lungs and spreads to other parts of the body, typically leading to poor prognosis and representing the majority of cancer deaths.
Step-by-step explanation:
Metastatic lung cancer refers to cancerous cells that have originated in the lung and then spread to other parts of the body. This dissemination occurs through mechanisms such as traveling via the blood to different sites, a process known as metastasis. These secondary tumors, known as metastases, can grow in various organs such as the brain, bones, and adrenal gland. The prognosis for metastatic cancer is often worse compared to cancers that have not spread, and it is associated with the majority of cancer deaths. Lung cancer itself arises from uncontrolled cell growth due to accumulated DNA damage, often caused by tobacco smoke, and is the leading cause of cancer-related deaths worldwide.