Pathology of the Head and Neck

Nasopharynx and Waldeyer’s Ring Chapter 6 173consisting of longitudinal folds on the dorsal wall of thenasopharynx around the 12–14th gestational week. Thedevelopment of the palatine tonsils begins with a proliferationof the endodermal epithelium of the second pharyngealpouch down into the surrounding mesenchyme,forming the epithelium-lined crypts. In the connectivetissue, mesenchymal cells of the second pharyngealpouch form so-called condensation centres. The firstprimary follicles can be localised around week 14. Theparafollicular areas develop into T-cell areas and precursorsof interdigitating cells can be identified. Aroundweek 16, the epithelium shows the first signs of cornification,and the lymphocytic infiltration of the epitheliumoccurs [59, 60].6.2 Nasopharynx6.2.1 Anatomy and HistologyThe nasopharynx is bordered anteriorly by the nasalchoanae and nasal cavities. The roof and posterior wallof the nasopharynx form an arch just below the base ofthe skull with the sphenoid sinus and the floor of thesella turcica. The postero-superior roof contains the(naso)pharyngeal tonsil. At its lower end in the posteriormidline lies a blind recess known as the pharyngealbursa. The lateral walls of the nasopharynx contain thepharyngeal ostia of the auditory tubes, which are surroundedby small aggregates of lymphoid tissue, thetubal tonsil. The cartilage of the auditory tube protrudesabove the ostium and is called the torus tubarius, behindwhich the Rosenmüller fossa is located. The floor ofthe nasopharynx is formed by the soft palate and uvula.The anterior and cranial portions of the nasopharynxare lined by respiratory mucosa with ciliated columnarepithelium with goblet cells and foci of metaplasticsquamous epithelium. Squamous mucosa predominatesin the lower nasopharynx adjacent to the oropharynx.Small seromucinous glands and aggregates of lymphoidtissue are present in the submucosa throughout the nasopharynxas a normal finding without qualifying as“chronic inflammation”.6.2.2 CongenitalDevelopmental AnomaliesCongenital developmental anomalies of the nasopharynxare rare and include choanal atresias and pharyngealstenosis. Bilateral occlusion has been reported inup to 40% of patients with choanal atresias. Bilateralatresias are typically osseous, unilateral atresias aremembranous. Pharyngeal stenosis is a paediatric disorderassociated with sleep apnoea and other craniofacialanomalies [108, 137]. Far more common are congenitalcysts and tumours arising from remnants of embryonictissue.6.2.2.1 NasopharyngealBranchial Cleft CystsNasopharyngeal branchial cleft cysts and fistulas arelocated in the lateral nasopharyngeal wall and can extendto the base of the skull through the parapharyngealspace. They occur unilaterally or bilaterally and have apostulated second pharyngeal arch origin. Most nasopharyngealbranchial cleft cysts are clinically silent duringchildhood and discovery may be delayed into earlyadulthood, when chronic inflammation induces proliferationof the lymphoid tissues. This produces a massresulting in respiratory difficulties and nasal obstruction.The cysts are lined with respiratory epithelium.Chronic irritation and inflammation induces squamousmetaplasia. Surgical specimens of nasopharyngeal cystsremoved for symptomatic disease may therefore showexclusively squamous epithelium and lymphoid hyperplasiain a fibrosed cyst wall [143, 177, 185].6.2.2.2 Tornwaldt’s CystA Tornwaldt’s cyst (or pharyngeal bursitis; named afterGustav Ludwig Tornwaldt, 1843–1910) is a dilatation of apersistent pharyngeal bursa in the posterior median wallof the nasopharynx above the superior pharyngeal constrictormuscles and at the lower end of the pharyngealtonsil caudally and posteriorly to where Rathke’s cleftcysts arise [128]. The cysts arise at the site of embryoniccommunication between the notochord and the roof ofthe pharynx and can be detected in up to 7% of adultsat routine autopsies [86]. Tornwaldt’s cysts are typicallyless than 1 cm in size and asymptomatic [92]. Obstructionof the bursal orifice results in a cystic dilatation.The cysts may become infected and inflamed with subsequentabscess formation. Symptomatic disease, termedTornwaldt’s disease, may present with nasal obstructionand nasopharyngeal drainage, dull occipital headaches,pain in the ears and neck muscles and occasionally neckmuscle stiffness [130]. Tornwaldt’s cysts are lined withtall, columnar, ciliated respiratory epithelium, but inflammationand infection induces squamous metaplasiaand fibrosis of the walls. Tornwaldt’s cyst may containvarying amounts of lymphoid tissue (Fig. 6.1). Most surgicalspecimens of symptomatic Tornwaldt’s cysts areeither devoid of an epithelial lining or lined with squamousepithelium.