Familial Nasopharyngeal Carcinoma 6

214 J. J. Lu, V. Grégoire, and S. Linlymph adenopathy, the anatomy of the nasopharynxand its adjacent structures, as well as the pattern oflymph node metastases so that the gross tumor volumes(GTV) and clinical target volumes (CTV) forsubclinical disease can be selected.In this framework, this chapter reviews the anatomyof the head and neck area with a focus onnasopharynx, its surrounding structures, and itsdraining cervical lymph nodes, and discusses theselection and delineation of both GTVs and CTVs inthe treatment of NPC.17.2AnatomyRosenmüller). The lateral walls harbor the pharyngealopening of the eustachian tube, and the cartilaginousextension of the opening with its mucosacoverage, which forms the torus tubarius. The pharyngealfossa lies just posterior to the torus tubariusand is formed by the junction of the lateral and posteriorwall of the nasopharynx (Figs. 17.1–17.3).One of the clinically important features of the anatomyof nasopharynx and its surrounding structurespertinent to NPC is the foramina and fissures locatedat the base of skull. Many of the foramina provide thepassage to the blood vessels and cranial nerves, andNPC may cause damage of the fossa of Rosenmüllerstructures located in these passages at its locallyDirect extension of the disease to the tissues andorgans close to the primary lesion is one of the mostimportant modes of disease spread, and lymph nodemetastases follow certain specific patterns in NPC. Adetailed discussion of imaging-based anatomy is outof the scope of this chapter. However, as the malignancyincluding its primary lesion and gross or subclinicallymph node metastasis is primarily treatedwith radiation therapy, a thorough understanding ofthe computer tomography (CT) or magnetic resonanceimaging (MRI) based anatomy of the head andneck area including cervical lymph node distributionis crucial for the accurate selection and delineationof the target volumes in IMRT for NPC.BA17.2.1Anatomy of the Nasopharynxand its Surrounding StructuresThe nasopharynx is a roughly cuboidal structure andis located below the central skull base. The roof of thenasopharynx is made of the sphenoid sinus and thebasisphenoid. The posterior part of the roof slopesinferiorly and is contiguous with the posterior wallof the nasopharynx, which is made of the clivus,together with the C1 and C2 vertebrae. The nasopharynxis contiguous with the nasal cavity anteriorlyand oropharynx inferiorly. The anterior border ofthe nasopharynx is the posterior nasal apertures andnasal septum, and the soft palate separates thenasopharynx from oropharynx inferiorly. The lateralwalls of the nasopharynx are formed by the medialpterygoid plate, the palatal muscle, the torus tubarius,and the pharyngeal fossa (also called the fossa ofNasopharynxLaryngopharynxOropharynxFig. 17.1. The lateral wall of nasopharynx. (A. Fossa ofRosenmüller; B. torus tubarius;