Pulmonary Disorders this section includes Chapter 75. Pulmonary Rehabilitation Chapter 81. A man aged 65 has a 50 times greater risk of developing lung cancer than a man aged 25, and a 3 to 4 times greater risk than men aged 45 to 64. The risk of lung cancer is related to the total years of smoking, which exposes smokers to carcinogens and promoting agents.
Risk also increases in the elderly because of the age-related decline in cellular DNA repair.
The four major histologic patterns of lung cancer are squamous cell carcinoma, adenocarcinoma, large cell carcinoma, and small cell carcinoma. Often, two or more of these patterns occur simultaneously. These tumors often grow slowly and usually arise in central airways. These tumors probably arise from bronchial and mucosal glands. Usually, it is distinguished by the absence of the distinctive characteristics of the other types.