Familial Nasopharyngeal Carcinoma 6

Selection and Delineation of Target Volumes in Intensity-Modulated Radiation Therapy for Nasopharyngeal Cancer 215a b cFig. 17.2. Normal anatomy of the nasopharynx. (a) AxialT1-weighted magnetic resonance imaging (MRI) demonstratesthe left eustachian tumor opening (arrow 1), fossaof Rosenmüller (arrow 2), and torus tubarius (arrow 3). (b)Coronal T1-weighted MRI demonstrates right torus tubarius(arrow 1), eustachian tube opening (arrow 2), and sphenoidsinus (3). (c) Sagittal T1-weighted MRI demonstrates the nasopharynx(N), sphenoid sinus (S), and soft palate (arrows).(Adopted from Chong and Ong [2008]. Used with permissionfrom Elsevier)is formed by the posterior margin of the petrous apexand the superior part of the clivus. Foramen ovale ispositioned lateral to the foramen lacerum (Fig. 17.4).17.2.2Classification of Lymph Node Levels in the NeckFig. 17.3. Transverse section of computer tomography (CT)through the nasopharynx at the level of the mandibularcondyle (k). The lateral pterygoid muscle (m) runs from thelateral pterygoid plate (black arrow) to the insertion alongthe medial aspects of the mandibular neck. Air is seen inthe eustachian tube close to the opening in torus tubarius(open arrow). The fossa of Rosenmüller is partly collapsed(arrowhead). (a internal carotid artery; v internal jugularvein; s styloid process) (Used with permission from Medcyclopaedia )advanced stage. The foramina and fissures also providepotential routes of intracranial extension. Of all theforamina and fissures, the foramen lacerum and foramenovale are the two important routes of intracranialextension from the primary disease. Foramen lacerumis located superolateral to the fossa of Rosenmüller, andThe head and neck region has a rich network of lymphaticvessels, and squamous cell carcinomas originatedfrom the head and neck area including NPCcan metastasize to regional cervical neck lymphnodes even in its early stages. Therefore, understandingof the normal anatomy of the neck lymph nodesis crucial for the treatment of head and neck cancers.To ensure effective communication, a standard terminologyis needed in the discussion of the complexlymph node regions. Various classifications havebeen developed for this purpose. Table 17.1 listed twoof the more commonly used terminologies/classification.For the purpose of radiation therapy for headand neck malignancies, the recommendation advocatedby the Committee for Head and Neck Surgeryand American Academy for Otolaryngology-Headand Neck Surgery (AAO-HNS) is one of the mostwidely utilized systems that is pertinent to radiationtherapy for NPC. This classification of the necklymph nodes (also called the “Robbins classification”)was originally proposed by the MemorialSloan-Kettering Cancer Group, and was adopted bythe AAO-HNS in 1991 and lately revised in 1998. Itsystematically classifies the neck nodes into six levelsaccording to visible structures including bone, muscle,