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Lung cancer is a malignant tumor that primarily originates in the lungs, or less frequently can originate in another organ and spread to the lungs through metastasis. Unfortunately, lung cancer is one of the most common and aggressive types of cancer.
Alright, now the lungs are these paired organs in the chest containing a collection of tubes and passages called the airways, which include the bronchi, then the bronchioles, the alveolar ducts, and finally the alveoli. The airways are lined by several types of epithelial cells that serve multiple functions.
These include columnar epithelial cells that have hair-like projections called cilia, which work to sweep foreign particles and pathogens up and out of the airways. Another type, called goblet cells, secrete mucin to moisten the airways and trap foreign pathogens. There are also club cells, sometimes called Clara cells, that secrete glycosaminoglycans to protect the bronchioles, and neuroendocrine cells that secrete hormones into the blood.
So, lung cancer occurs when any of these epithelial cells acquire mutations, which can arise due to a variety of risk factors. Environmental risk factors include exposure to toxins like tobacco smoke, air pollution, asbestos, coal dust, radon gas, or ionizing radiation. There are also some genetic risk factors, where few clients are genetically predisposed to develop lung cancer even without the presence of environmental risk factors.
So, once an epithelial cell becomes mutated and cancerous, it starts dividing uncontrollably, forming a tumor mass. As the tumor keeps growing, new blood vessels also develop via angiogenesis to supply it. Eventually, cancerous cells start invading neighboring tissues, and may even spread to nearby lymph nodes or metastasize to distant organs, such as the brain, bones, or liver.
Now, there are two main types of lung cancer, non-small cell and small cell. Non-small cell lung cancers account for most lung cancers, and there’s different subtypes depending on the cell of origin. The most common one is adenocarcinoma, which usually develops at the periphery of the lung from the goblet cells; another quite common one is squamous cell carcinoma, which is usually centrally located in the lungs, and originates from mutated columnar epithelial cells that become squamous epithelial cells.
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