Pathology of the Head and Neck

Nasopharynx and Waldeyer’s Ring Chapter 6 183grade carcinoma of salivary gland origin because theydo not metastasise.6.2.7 Malignant Non-EpithelialTumours of the Nasopharynx6.2.7.1 ChordomaICD-O:9370/3Chordomas are tumours arising from remnants of thenotochord in the axial skeleton near its cranial and caudalends. The cranially located chordomas compriseabout one-third of all chordomas, arise earlier than thesacral chordomas, around the 3rd to the 5th decade andin children. Most chordomas in nasopharyngeal locationare extensions of cranial chordomas, but they rarelyarise de novo in the nasopharynx and paranasal sinuses[19, 34, 54]. For a more detailed description of chordoma,see Chap. 4.6.2.7.2 SarcomaThe most common sarcoma in the head and neck areais the rhabdomyosarcoma, specifically the embryonalrhabdomyosarcoma (ICD-O:8910/3) in children lessthan 5 years of age [49]. Primary nasopharyngeal rhabdomyosarcomasare rare [20, 39, 50] as are primary nasopharyngealchondrosarcomas (ICD-O:9220/3) [54,56]. Case reports of primary nasopharyngeal sarcomasinclude an osteosarcoma in an 11-year-old girl aftermulti-agent chemotherapy and radiation treatment of aretinoblastoma, a liposarcoma and a granulocytic sarcomain a 37-year-old Chinese man [5, 42, 139]. The folliculardendritic cell sarcoma, a tumour of antigen-presentingcells of B-follicles of lymphoid tissues, is commonlyfound extranodally in the head and neck area, butrarely in the nasopharynx [10, 22, 23]. It is characterisedby positivity for CD21, CD35 and CD23, as well as indolentclinical behaviour and a low risk of recurrence andmetastasis [87].6.3 Waldeyer’s Ring6.3.1 Anatomy and Histologyof Waldeyer’s RingThe term Waldeyer’s ring refers to the ring of lymphoidtissues occurring in the nasopharynx and oropharynx.The oropharynx is separated from the nasopharynxby the oropharyngeal isthmus, which is formed by themerging muscular pillars of the palatoglossal and thepalatopharyngeal muscles. In the lateral walls, at thewidest points of the pharynx, lies the triangular tonsillarfossa, which contains the palatine tonsil. The tonsilsof Waldeyer’s ring belong to the gut-associated lymphoepithelialorgans, which show a close morphological andfunctional correlation between lymphatic tissue of mesenchymalorigin and the endodermal epithelium of thesecond pharyngeal pouch. The Waldeyer’s ring tonsilsare composed of the paired palatine tonsils in the tonsillarfossa, the unpaired (naso)pharyngeal tonsil in theroof of the nasopharynx, the bilateral tubal tonsils in thelateral walls of the nasopharynx at the entrance to theauditory tube and the lingual tonsil in the retrolingualregion. Lymphoid aggregations close to the epiglottis arealso counted as part of Waldeyer’s ring.The palatine tonsils are the largest of the tonsils andlie in the tonsillar fossa along the anterolateral borderof the oropharynx between the palatoglossal and palatopharyngealmuscle arches. The lateral surface of thepalatine tonsil has a fibrous capsule, but skeletal musclefibres and islands of mostly elastic cartilage are normalfindings there. The medial surface has 10–30 epithelium-lined,extensively branching and anastomosing tonsillarcrypts that extend deeply into the lymphoid tissue.The surface of the palatine tonsils is lined by stratifiedsquamous epithelium, the crypts are covered by nonkeratinisingstratified (“transitional-type”) epitheliumwith a discontinuous basement membrane and numerousintraepithelial lymphoid cells. This so-called lymphoepitheliumrepresents the specialised epithelium ofthe tonsils and contains M-cells (resembling the intestinalmembranous [M] cells of the Peyer’s patches), T- andB-cells, and patchily distributed macrophages and dendriticcells [140, 152]. The surface epithelium is evenlyinfiltrated by T-cells and B-cells; up to 30% of the intraepithelialT-cells are T-cells, which are involved inantigen recognition independent of MHC restrictionand prior antigen processing [66, 149]. A clustering ofCD4+ T-cells with B-cells is typical within the lymphoepitheliumof the crypts and in the submucosa [66]. Thesubmucosal lymphoid tissue contains numerous primaryand secondary lymph follicles with germinal centres,a mantle zone and a network of follicular dendritic cells.T-cells, interdigitating dendritic cells, plasma cells, macrophagesand high-endothelial venules are found in theextrafollicular regions [140]. The palatine tonsils haveno afferent lymph vessels. The rich efferent lymphaticdrainage is via the retropharyngeal lymph nodes to theupper deep cervical lymph nodes.The small unencapsulated (naso)pharyngeal tonsilwith about 12–15 shallow crypts is lined with a columnarciliated respiratory surface epithelium with numerousgoblet cells, which may also be seen in the lymphoepitheliallining of the short and plump crypts [200]. Thelymphoid tissue contains numerous lymph follicles withgerminal centres. Minor salivary glands in the periph-