Smoker's Lung: Pathology Photo Essay (cont.)
Michael C. Fishbein, MD
Dr. Fishbein received his undergraduate and medical degrees from the University of Illinois. He completed a residency in anatomic and clinical pathology at Harbor General Hospital/UCLA Medical Center. He is board certified in anatomic and clinical pathology.
In this Article
- Smoker's lung introduction
- What is the structure of the normal lung?
- What processes determine normal function of the lung?
- What are the abnormalities (diseases) in smoker's lung?
- What happens to the lung in emphysema?
- How does emphysema come about?
- Why does smoker's lung look black?
- What happens to the airways in chronic bronchitis?
- Are smokers with COPD predisposed to developing pneumonia?
- What about lung cancer in smokers?
- Are any of the pulmonary consequences of smoking reversible?
- From what do smokers die?
Are smokers with COPD predisposed to developing pneumonia?
The answer is yes. As previously mentioned, smoking increases mucus production and impairs the clearing action of the cilia in the airway. Also, the addition of bacteria, inflammatory cells, and damaged lung cells to the secretions in the airway and lung make the secretions especially thick, tenacious, and difficult to clear. Therefore, in such a stagnant and nutritious (the mucus) environment, bacteria can flourish and cause infection of the lung (pneumonia). Furthermore, even the inflammatory cells are damaged by tobacco smoke so that their ability to fight infection is diminished.
For all of these reasons, pneumonia is not only more common, but it is often also more severe in smokers with COPD (chronic obstructive pulmonary disease, that is, emphysema and/or chronic bronchitis) than in non-smokers without COPD. Moreover, the inflammatory cells that accumulate in the lung to fight off the infection can fill the alveolar spaces and thereby further limit diffusion of oxygen and carbon dioxide. Therefore, smokers with COPD, who already have impaired breathing (pulmonary function), often become much worse when there is a superimposed infection of the lung (pneumonia). Figure 7 is a microscopic section of a lung with pneumonia in a patient with COPD.
Notice that most of the alveoli are filled with inflammatory cells. Some alveoli, however, are unaffected and empty because the involvement of this lung with pneumonia is patchy.
What about lung cancer in smokers?
Smoke contains more than 60 carcinogens (chemicals that cause cancer) and about 200 known toxic substances. Scientists are still learning about how carcinogens work and why only some people who smoke get lung cancer. Genes are the hereditary units in chromosomes and appear to have a lot to do with a person's susceptibility to cancer. The genes are made up of DNA (deoxyribose nucleic acid), which controls how cells divide and reproduce (proliferate). Damage to DNA from cigarette smoke can lead to uncontrolled cell proliferation and growth, which is what cancer is finally all about.
It is of interest that some smokers develop COPD, some develop lung cancer, some get neither, and some get both. We really don't know the reason for these different susceptibilities. Besides that, lung cancer from smoking can take a number of different forms. For example, the cancer cells can resemble cells of the skin (squamous cell carcinoma), cells of the bronchial glands (adenocarcinoma), or specialized cells of the nervous system (neuroendocrine carcinoma). Figure 8 shows an adenocarcinoma in a smoker's lung with severe emphysema.
What do you think the outcome (prognosis) is for this patient with lung cancer? Well, almost all types of lung cancer are particularly deadly. Thus, if a lung cancer is more than an inch or so in diameter (as in this patient) or has spread outside of the lung, fewer than 50% of affected individuals will survive another 5 years. And that is even with the best of therapy. What's more, consider a cancer that is less than an inch in size (or not large enough to be seen on a chest X-ray) and is confined to the lung. Unfortunately, even if such a cancer is completely removed by surgery, about 25% of individuals will still die from the cancer in less than 5 years from the time of diagnosis. The reason for this poor outcome (prognosis) is that lung cancers tend to spread (metastasize) early in the course of disease to other organs, most often the brain, liver, and bone.
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