**7. Staging of NPC**

After the initial diagnosis of NPC is made on history, physical examination, and biopsy, cross-sectional imaging is required for cancer staging. Currently, the 7th edition of the International Union Against Cancer (UICC) and American Joint Committee on Cancer (AJCC) TMN staging system is used, which was recently revised and released on 1 January 2010. As previously described, most cases of NPC originate in the lateral pharyngeal recess and spread submucosally with early infiltration into deeper neck spaces. NPC tends to have well-defined patterns of spread.

Imaging of Nasopharyngeal Carcinoma 105

Stage T1 refers to disease that is localized to the nasopharynx, as well as disease that has extended inferiorly into the oropharynx or anteriorly into the nasal cavity (Lee,2004; Liu *et al.,* 2008; Yu *et al.,* 2010). Disease that is isolated to the NP is described as being superficial to the pharyngobasilar fascia (PBF). In this case, there is no evidence of tumour breaching or crossing the PBF barrier, which occasionally can be identified on T2-weighted studies as a thin dark curvilinear line running from the medial pterygoid plate laterally and following the contour of the longus musculature along the back wall of the NP (**Figure 3).** The tumour appears as a hypointense to isointense mass on T1-weighted imaging that enhances to a

Oropharyngeal extension is readily noted on coronal or sagittal MR imaging as tumour that has extended inferiorly past the plane of palate (**Figure 5)**. On axial sections, the oropharynx

Fig. 5. Axial image of a patient with NPC that shows disease that has extended down to the

In addition, stage T1 disease comprises anterior extension past the plane of the posterior choana into the nasal cavity (**Figure 6)**. From the nasal cavity, NPC can invade through the sphenopalatine foramen into the pterygopalatine fossa (stage T3 disease), resulting in obliteration of the normal fat content in this fossa (**Figure 7).** Direct extension from the nasal cavity is the most common route of NPC invasion into the pterygopalatine fossa, followed

is considered involved when tumour is seen inferior to the C1/C2 junction.

lesser degree than normal mucosa (Chin *et al.*, 2003).

level of the right oropharynx.

**7.1 T1 NPC** 


Box 1.
