Pharyngeal (Throat) Cancer & its types

The term “throat cancer” can refer to either cancer of the pharynx or the larynx. Pharyngeal cancer occurs when cells in the pharynx become malignant and aggregate to form a tumor.

About the Pharynx

The pharynx is typically divided into three parts:

• Nasopharynx – the upper part of the throat located behind the nasal cavity and above the soft palate.
• Oropharynx – the middle part of the throat that lies behind the oral cavity.  This is the part of the throat you can readily see when looking in the mirror. It allows food and fluids to pass from the mouth to the esophagus and air to flow into the lungs via the trachea.
• Hypopharynx (sometimes called laryngopharynx) – the lower part of throat located behind the oropharnyx and adjacent to the larynx. It helps in swallowing and prevents aspiration.

All parts of the pharynx, along with the nasal cavity and paranasal sinuses, act as resonating chambers for sounds produced by the vocal cords in the larynx.

Nasopharyngeal Cancer
Nasopharyngeal cancer is different from other pharyngeal cancers in several significant ways:

• It is much more prevalent within Asian and Southeast Asian populations, with highest incidence in Southern China (Guangdong Province) and Taiwan
• It is strongly correlated with infection by Epstein-Barr virus (EBV)
• Some types are highly radiosensitive, and radiotherapy is the preferred treatment

Most nasopharyngeal cancers are squamous cell carcinomas. These can be subdivided into several forms, which vary in terms of cellular differentiation:

• Keratinizing
• Well-differentiated cells that produce keratin
  • More common in the United States; less common in Asia
  • Less associated with EBV infection
  • May be associated with traditional risk factors of head and neck squamous cell carcinoma such as tobacco use
  • Less radiosensitive and more radioresistant
  • Tends not to metastasize to distant sites, but is frequently locally invasive
  • • Non-keratinizing (cells do not produce keratin)
      • Moderately-differentiated subtype
        • Tends to metastasize to regional lymph nodes
        • Variable radiosensitivity
        • Often linked to EBV infection
      • Undifferentiated subtype
        • Often occurs in conjunction with high numbers of lymphocytes, and may also be called lymphoepithelioma
        • More common in Asia
        • Most often associated with EBV infection
        • Tends to metastasize to regional lymph nodes
        • Very radiosensitive
    Oropharyngeal Cancer
    
    Like other pharyngeal cancers, most oropharyngeal cancers are squamous cell carcinomas. Sites within the oropharynx that may develop cancer are:
    • Base of the tongue
    • Tonsillar region (the most common site for primary cancers of the oropharynx)
    • Soft palate, which includes the uvula
    • Pharyngeal walls
    • Risk Factors for Oropharyngeal Cancer
      • Tobacco (both chewed and smoked) is strongly linked to developing oropharyngeal cancer.
      • Poor nutrition, specifically a diet low in fruits and vegetables that result in few dietary antioxidants
      • Heavy alcohol consumption
      • Eastern Asian decent
      • HPV (human papillomavirus) has been implicated as a major factor in the disease, with transmission occurring through oral sex.
      Hypopharyngeal Cancers
      Hypopharyngeal cancers are the least common type of pharyngeal cancer. Again, almost all cancers of this type are squamous cell carcinomas.
      Risk Factors for Hypopharynceal Cancer
      • Excessive drinking
      • Smoking
      • Poor nutrition, specifically a diet low in fruits and vegetables that result in few dietary antioxidants
      • Male gender
      • HPV (human papillomavirus). While HPV is much more prevalent in oropharyngeal cancers, it has been found in some hypopharyngeal cancer patients. Its significance in the development of this cancer is unknown.