If untreated, lung cancer will, almost without exception, lead to metastasis due to invasion of lymph or blood vessels.
Lymphogenic spread is the most common primary route.
- Tumors in the lower lobe usually drain via the posterior mediastinum to the subcarinal lymph nodes.
- Tumors in upper right lobe usually drain to the upper mediastinum.
- Tumors in the upper left lobe usually drain to the anterior mediastinum, as well as to the upper mediastinum in 1/3 of the cases.
- Retrograde lymph drainage to the pleura can occur, especially from peripheral tumors.
Hematogenic spread to other organs also occurs frequently.
The most common localizations are:
- other lobe of the lungs
- adrenal glands
The primary tumor can also spread by direct invasion of neighboring organs, such as mediastinal pleura, diaphragm, chest wall, or vertebrae.