Familial Nasopharyngeal Carcinoma 6

90 C. K. Ong and V. F. H. ChongabFig. 8.11. 39-year-old female presented with left cervicallymphadenopathy. (a) Axial contrast-enhanced fat-saturatedT1-weighted MR image shows a small nasopharyngeal carcinomaarising from the left lateral pharyngeal recess (blackarrow). An adjacent necrotic retropharyngeal node is evident(white arrow). (b) Axial contrast-enhanced fat-saturated T1-weighted MR image more inferiorly shows multiple enlargedcervical nodes (arrows), despite the small and seemingly localizedprimary tumor. One of the nodes is necrotictumor cells along the lymphatic system and hasprognostic significance. The internal jugular nodesmay be viewed as successive defensive barriers, withthe supraclavicular nodes being the last line ofdefense. Failure of supraclavicular nodes to containthe malignant cells results in them spilling into thethoracic duct and eventually the systemic circulation.Supraclavicular lymphadenopathy (N3 disease) istherefore associated with a high risk of systemicmetastasis.8.3.5Staging: Systemic MetastasisNPC has a relatively high incidence of systemic metastasis(up to 41%) when compared with the other headand neck tumors (5%–24%). The most common sitesof metastases are bone (20%), lung (13%), and liver(9%) (Sham et al. 1990).The risk of systemic metastasis increases in individualswith more advanced primary tumors and/orextensive lymph node involvement. Advanced tumorsinfiltrating the parapharyngeal space are related tohigher incidence of systemic metastasis (Xiao et al.2002). Tumor invasion of the parapharyngeal veins(which drain via the retropharyngeal and facial veinsinto the internal jugular vein) results in disseminationof disease through the systemic circulation. Inaddition, (Kumar et al. 2004) showed that there wasa direct correlation between the prevalence of distantmetastasis and the N-classification as well as theoverall stage of NPC. The positive yield of their metastaticwork-up (chest X-ray, liver ultrasound, andwhole body bone scan) was 0, 1.8%, 4.8%, and 14.3%for N0, N1, N2, and N3 disease, respectively.Imaging surveillance (which may include chestX-ray or CT of the thorax, ultrasound or CT of theabdomen, and whole body bone scan) is indicated inpatients with advanced disease who are more susceptibleto metastasis. On the other hand, as the probabilityof systemic metastasis is relatively low inpatients with early NPC (stage I and II) diseases, thevalidity of metastatic work-up in every single patientdiagnosed with NPC is debatable.There is some evidence that fludeoxyglucosepositron emission tomography (FDG-PET) or PET/CT has a higher sensitivity and specificity in detectingvisceral and skeletal metastases when comparedwith CT thorax and abdomen and whole body radioisotopebone scan, respectively (Liu et al. 2007;Chua et al. 2009; Ng et al. 2009). Nevertheless, therole of PET or PET/CT in the detection of systemicmetastasis and staging of NPC is yet to be fullyestablished.8.3.6Differential DiagnosisSeveral other tumors, albeit much less common, mayarise from the nasopharynx. At times, it may be impossibleto differentiate these tumors from NPC on imagingalong, and histologic confirmation is necessary.