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Laryngeal cancer is a malignant tumor that originates from the larynx, which is the part of the throat used for swallowing and talking.
First, let’s quickly review the anatomy and physiology of the larynx, which is located in the upper portion of the neck between the pharynx and the trachea. Now, the larynx can be divided into three main parts. The upper part, or the supraglottis, is located below the base of the tongue and includes the epiglottis, which closes off during swallowing, preventing food and liquids from entering the airway.
Next is the middle part, or glottis, which contains the vocal cords. When these are closed, air pressure builds up below them, causing them to vibrate and produce sound when we speak. Finally, the lower part, or subglottis, extends between the vocal cords and the start of the trachea.
Now, the larynx is lined with a stratified squamous epithelium which then transitions into a pseudostratified ciliated columnar epithelium. This contains goblet cells, which produce mucus to trap small foreign particles; as well as columnar cells, which have cilia, or tiny little hair-like projections that move mucus up the respiratory tract so it can be coughed out.
All right, now, laryngeal cancer occurs when any of these epithelial cells acquire mutations, which can arise due to a variety of risk factors. Modifiable risk factors include exposure to irritants, such as tobacco smoke, alcohol, asbestos, coal dust, and ionizing radiation. Other modifiable risk factors include obesity, infection with human papillomavirus, or HPV, as well as a history of gastrointestinal reflux disease, where acid from the stomach goes all the way up the esophagus into the pharynx. From there, the acid can contact and irritate the larynx. As for non-modifiable factors, few clients with a family history of laryngeal cancer are genetically predisposed to develop this type of cancer even without the presence of environmental risk factors.
So, chronic exposure to irritants can cause the normal columnar cells to undergo dysplasia, or abnormal growth. Depending on how much of the epithelium is affected by dysplasia, it can be divided into three grades. The higher the grade, the more likely the lesion will evolve into cancer. Eventually, if the irritation persists, dysplasia can evolve into carcinoma in situ, which affects the entire thickness of the epithelium. Finally, carcinoma in situ can progress to invasive laryngeal carcinoma, which is when cancerous cells break through the epithelial basement membrane into the underlying stroma, and may even spread to nearby lymph nodes or metastasize to distant organs, such as the lung, bones or liver.
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