What defines extensive-stage small cell lung cancer?

Extensive-stage small cell lung cancer (SCLC) is characterized by the cancer having spread beyond its initial site in the lung and involves distant organs. This spread indicates a more advanced and aggressive form of the disease, where the cancer cells have left the localized area and infiltrated other tissues or organs, which can include the liver, bones, or brain. Such involvement significantly influences treatment options and prognosis.

The other options describe forms of lung cancer that are either localized or limited to a specific area. Cancer confined to a single hemithorax or a single radiation portal suggests a more localized disease, which would be representative of limited-stage disease. Similarly, localized without lymph node involvement implies a potentially earlier stage of the cancer that does not yet warrant the extensive classification.