lungcancer

Lung cancer is a malignant tumor that begins in the lungs. It is the leading cause of cancer death worldwide. It is traditionally divided into non-small cell lung cancer (NSCLC), which accounts for about 85%, and small cell lung cancer (SCLC), about 10–15%.

NSCLC includes adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. SCLC tends to grow quickly and spreads early. Combined histology can occur.

Risk factors include tobacco smoke, secondhand smoke, exposure to radon gas, occupational carcinogens such as asbestos and diesel exhaust, air pollution, prior chest radiation, and certain genetic factors. The risk declines after smoking cessation, but cumulative exposure still influences risk.

Symptoms may include a persistent cough, coughing up blood, chest pain, shortness of breath, hoarseness, unexplained weight loss, and fatigue. Early-stage disease may not cause symptoms. Diagnosis typically involves imaging (X-ray, CT, PET) and confirmation by tissue biopsy with histology and molecular testing for mutations.

Staging uses the TNM system for NSCLC (I–IV). SCLC is often categorized as limited vs extensive disease. Treatment depends on stage and biology: surgery and/or radiotherapy for early NSCLC; systemic therapies (chemotherapy, targeted therapy for mutations such as EGFR, ALK, ROS1; immunotherapy) for advanced disease. SCLC commonly receives chemotherapy and radiotherapy; immunotherapy is increasingly used in extensive-stage disease.

Prognosis varies with stage, histology, and response to therapy. Five-year survival is higher with early detection. Prevention focuses on avoiding tobacco exposure, reducing radon, and protecting against occupational carcinogens. Screening with low-dose CT is recommended for high-risk individuals in some guidelines.