Familial Nasopharyngeal Carcinoma 6

Imaging in the Diagnosis and Staging of Carcinoma of Nasopharynx 83in the pharyngobasilar fascia, known as the sinus ofMorgagni. The eustachian tube opens anterior (onaxial images) and inferior (on coronal images) to thetorus tubarius (distal cartilaginous end of the eustachiantube). The lateral pharyngeal recess (fossa ofRosenmuller) is seen posterior (on axial images) andsuperior (on coronal images) to the torus tubarius,partly due to the inverted J-configuration of the torustubarius (Fig. 8.1). The lateral pharyngeal recess is themost common site of origin of NPC. However, theserecesses can be notoriously asymmetric in normalindividuals, which should not be mistaken as tumors.The parapharyngeal space is located lateral to thenasopharynx, separating it from the masticator space(Fig. 8.1). Displacement or obliteration of the parapharyngealfat serves as an important marker of tumorinfiltration. The carotid space is located posterior tothe parapharyngeal space and forms the posterolateralborder of the nasopharynx. Between the nasopharyngealmucosal space and the prevertebral musclesis the retropharyngeal space, within which are themedial and lateral retropharyngeal nodes. The lateralretropharyngeal nodes (nodes of Röuviere) constitutethe first echelon nodes in the lymphatic drainage ofthe nasopharynx. The medial retropharyngeal nodesare less often visible on imaging.8.3Imaging in Diagnosis and Staging ofNasopharyngeal Carcinoma8.3.1Imaging Issues and FeaturesMulti-planar magnetic resonance imaging (MRI),using a dedicated head and neck coil, is the modalityof choice for evaluation of NPC. Axial and coronalcontrast-enhanced T1-weighted images with fat saturationallow precise mapping of the tumor (notablyperineural and intracranial spreads), and thus accuratestaging of the disease (Tables 8.1 and 8.2) (Chonget al. 1999; Lau et al. 2004). Bone-algorithm computedtomography (CT) is valuable in depicting early skullbase cortical bone erosions.NPC is generally isodense to muscle on nonenhancedCT. It is usually hypo- to isointense and relativelyhyperintense to muscle on T1-weighted andT2-weighted MR images, respectively. Mild to moderatetumor enhancement is evident following intravenouscontrast on both CT and MRI.Table 8.1 Nasopharyngeal carcinoma: sixth edition TNM classification(2002)T – primary tumorT1T2T2aT2bT3T4N – regional lymph nodesNxN0N1N2N3N3aN3bTumor confined to nasopharynxTumor extends to soft tissueof oropharynx and/or nasal fossaWithout parapharyngeal extensionWith parapharyngeal extensionTumor invades bony structures and/orparanasal sinusesTumor with intracranial extensionand/or involvement of cranial nerves,infratemporal fossa, hypopharynx or orbitRegional lymph nodes cannot be assessedNo regional lymph node metastasisUnilateral lymph node(s) metastasis,6 cm or less in greatest dimension, abovesupraclavicular fossaBilateral lymph nodes metastasis,6 cm or less in greatest dimension,above supraclavicular fossaLymph node(s) metastasis greater than6 cm in dimensionLymph node(s) metastasis in thesupraclavicular fossaTable 8.2 Nasopharyngeal carcinoma: stage groupingStage 0 Tis N0 M0Stage I T1 N0 M0Stage IIA T2a N0 M0Stage IIB T1 N1 M0T2a N1 M0T2b N0, N1 M0Stage III T1 N2 M0T2a, T2b N2 M0T3 N0, N1, N2 M0Stage IVA T4 N0, N1, N2 M0Stage IVB Any T N3 M0Stage IVC Any T Any N M1