Nasopharyngeal Carcinoma (NPC)

👉Nasopharyngeal carcinoma (NPC) is rare in the Western Hemisphere, showing its highest incidence in the Alaskan Eskimo and Mediterranean populations; however, it is endemic in southern China.

• The etiology of NPC is multifactorial and has:
  • Viral, genetic, and environmental factors

• Undifferentiated subtype of NPC:
  • Is strongly associated with Epstein-Barr virus (EBV):
    • EBV is also associated with earlier lesions:
      • Such as carcinoma in situ
• The nasopharynx extends anteriorly from the posterior choana of the nasal cavity to the free border of the soft palate:
  • It comprises a:
    • Vault
    • The lateral walls:
      • Including the fossa of Rosenmüller and mucosa covering the torus tubarius
    • A posterior wall
    • The superior surface of the soft palate:
      • Which is the floor
  • The posterior lip of the opening of the Eustachian tube is the torus tubarius:
    • Behind which is a mucosal fold:
      • Called the fossa of Rosenmüller

• The World Health Organization (WHO) classification for NPC encompasses:
  • Keratinizing SCC
  • Nonkeratinizing carcinomas:
    • Well differentiated
    • Undifferentiated
  • Basaloid squamous cell carcinoma

• Keratinizing SCC (type 1):
  • Is more common in North America:
    • Not associated with EBV
• Nonkeratinizing carcinoma, undifferentiated type (type 2b):
  • Is highly associated with EBV
  • Accounts for 60% of all NPCs in adults
  • The most frequent type in the pediatric population
• The first-echelon lymphatic drainage of NPC includes the :
  • Retropharyngeal lymph nodes
  • Superior jugular lymph nodes
  • Posterior cervical chain nodes

• Lymph node metastasis from NPC is common:
  • As many as 90% of patients:
    • Have evidence of unilateral nodal involvement
  • As many as 50% of patients:
    • Have evidence bilateral nodal involvement
• The nasopharynx is the upper one-third of the pharynx and is separated from the oropharynx below by the soft palate:
  • Anatomically:
    • It is the space situated behind the nasal cavities
    • Its mucosal lining starts immediately behind the posterior choana
    • It is actually located in the center of the head:
      • It is located more than 10 cm from the skin surface of the head in all directions
    • The undersurface of the body of the sphenoid bone:
      • Forms the roof (vault) of the nasopharynx:
        • Which slants downwards to form the posterior wall of the nasopharynx:
          • In front of the arch of the atlas and upper part of the body of the axis vertebrum
    • The floor of the nasopharynx:
      • Is formed by the upper surface of the soft palate:
        • Which separates the nasopharynx from the oropharynx below
      • The lateral wall of the nasopharynx is formed by:
        • The opening of the Eustachian tubes superiorly
        • The upper part of the superior pharyngeal constrictor muscle inferiorly
        • The orifice of the Eustachian (auditory tympanic) tube is delineated by:
          • An incomplete cartilaginous ring:
            • The deficient portion is in the inferolateral aspect
            • The medial portion of the cartilaginous ring:
              • Elevates the overlying mucosa to form the medial crusa:
                • Also known as the Torus tubarus
              • The slit-like space formed by this medial crusa and the posterior wall of the nasopharynx:
                • Is the fossa of Rosenmüller

• The muscular wall of the nasopharynx is formed by the:
  • Superior pharyngeal constrictors lying deep to the pharyngobasilar fascia:
    • The fascial sheets join:
      • To form a median raphe:
        • Which extends from the skull base downwards along the entire posterior pharyngeal wall
• The lymph nodes that drain the nasopharynx:
  • Lie in the retropharyngeal space:
    • Outside the pharyngobasilar fascia
    • In front of the prevertebral fascia
• The cranial nerves IX, X, XI and XII, the carotid sheath and the sympathetic trunk:
  • Traverse the parapharyngeal space:
    • Which is lateral to the superior pharyngeal constrictor
• The roof (vault) of the nasopharynx:
  • Is lined by pseudostratified ciliated epithelium
• The posterior wall of the nasopharynx:
  • Is lined with stratified squamous cells:
    • The epithelium has a well-defined basement membrane and there is abundant lymphatic tissue in the lamina propria:
      • This lymphoid tissue forms the pharyngeal tonsil or adenoid in children
• Branches of the internal maxillary artery:
  • Supply the nasopharynx
• Venous drainage is to the:
  • Pterygoid venous plexus:
    • Then to the facial and internal jugular veins
• The sensory nerve supply of the region:
  • Is from branches of the maxillary nerve (V2)
• The lymphatic supply of the nasopharynx drains into the retropharyngeal lymph nodes:
  • Efferent lymphatics from these nodes and those that come directly from the nasopharynx:
    • Drain to the deep cervical lymph nodes:
      • The lymphatic drainage then passes down the neck nodes in an orderly fashion:
        • From the high neck nodes to the lower ones

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