Cigarette smoking is the leading cause of lung cancer, responsible for approximately 85% of all cases. The carcinogens in tobacco smoke cause mutations in lung epithelial cells, leading to uncontrolled cell growth and tumor formation. This direct exposure makes lung tissue especially vulnerable compared to other organs. Smoking cessation significantly reduces lung cancer risk, highlighting the strong causal relationship. Other cancers have weaker or less direct associations with smoking.

Reference: Harrison’s Principles of Internal Medicine, Fauci et al., 20th Edition.