Smoker's Lung: Pathology Photo Essay (cont.)
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.
Figure 8: SMOKER'S LUNG WITH EMPHYSEMA AND CANCER
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 so 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.
Next: Are any of the pulmonary consequences of smoking reversible? »
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