– The major histologic types of lung cancer are non–small cell cancers (squamous cell cancer, adenocarcinoma, and large cell undifferentiated cancer), which account for 90% of lung cancers, and small cell lung cancers, which make up the remaining 10%.
Causes and Incidence
Cigarette smoking is implicated in approximately 80% to 90% of all cases of lung cancer. Occupational exposure to asbestos, radon, nickel, chromium, hydrocarbons, and arsenic is linked to 10% to 15% of lung cancers. The role of air pollution and home exposure to radon gas is unclear. Lung cancer is the leading cause of cancer death for both men and women in the United States. More than 170,000 cases are diagnosed each year, and the incidence for women is rising rapidly.
Squamous cell carcinomas usually begin in the larger bronchi, often causing bronchial obstruction and spreading by direct extension and lymph node metastasis. Adenocarcinomas are peripheral tumors that begin in fibrotic lung tissue and spread through the bloodstream, commonly metastasizing to the brain, liver, and bone. Large cell undifferentiated carcinoma, which may arise in any area of the lung, disseminates early, spreading through the bloodstream. Small cell carcinoma is centrally located and is the fastest growing type of lung cancer, with rapid metastasis to the brain, liver, and bone.
A chronic cough, a change in the volume and color of sputum, chronic upper respiratory tract infections, and aching in the chest are common presenting symptoms. Wheezing, fatigue, and chest tightness may also be present.
The prognosis is poor. The long-term survival rate in individuals with localized disease is only 35%, and most people have extension and metastasis upon diagnosis. Overall the survival rate for all individuals regardless of stage is 13%. Complications include superior vena cava syndrome, paraneoplastic syndromes, and cor pulmonale.
A history of smoking and a chest x-ray are the principal sources of diagnostic suspicion. A sputum cytology test is positive in about 75% of cases. Retrieval of cells through bronchoscopy or needle or tissue biopsy provides the definitive diagnosis.
Resection of tumor and surrounding tissue; lobectomy or pneumonectomy.
Systemic multidrug combination chemotherapy; biologic response modifiers.
Radiotherapy before and after surgery and for palliation; smoking cessation; prevention through education about dangers of tobacco and environmental irritants.