Most cases caused by prolonged heavy smoking . Industrial exposure to radioactive isotopes and asbestos also important. Stage III involves pleura, other adjacent structures, contralateral mediastinal or distant nodes.
Metaplastic change is reversible if smoking ceases.
Carcinomas may exfoliate into sputum, and are reliably diagnosed by cytology from bronchial brushings, alveolar lavages and submucosal aspirates. Bronchial carcinoids grow as endobronchial polyps. They are rare, resectable, rarely metastasize, but may stubbornly recur locally, with perineural spread over many years. Primary lymphoma of lung takes 2 forms. Prognosis with therapy is good.