Familial Nasopharyngeal Carcinoma 6

46 S. S. Lo and J. J. Luand the clivus. There are multiple foramina in thebase of skull that can serve as the portals of entryinto the cranium. The tumor can gain access to thecavernous sinus and the middle cranial fossa, invadingcranial nerves II–VI through the foramenlacerum, which is located immediately above thefossa of Rosenmüller. The tumor can gain accessto the middle cranial fossa, the petrous temporalbone, and the cavernous sinus through the foramenovale. Posterior extension of NPC can resultin direct invasion of the prevertebral muscles.4. Inferior spread – Inferior extension of NPC intothe oropharynx can occur. However, direct involvementof the soft palate is relatively uncommon.4.5.3Regional Nodal SpreadLymphatic spread to the ipsilateral neck occurs in85–90% of cases and to bilateral neck in 50% of thecases (Lee and Fu 2004; Lindberg 1972; Mao et al.2008; Ng et al. 2004). It is uncommon to see contralateralcervical nodal metastasis alone. The lateraland medial retropharyngeal lymph nodes areregarded as the first echelon nodal stations forNPC. Because of their deep location, retropharyngealnodal metastases are not palpable. Metastaticinvolvement of jugulodigastric (Level II) and superior/posteriorcervical nodes (upper Level V) is alsovery common. Some oncologists also consider levelII as first echelon nodes. Further nodal metastasisproceeds in the craniocaudal direction. In patientswith very extensive cervical nodal metastases, spreadto unusual lymph node locations like the submentaland occipital regions can occur due to lymphaticchannel obstruction. Mediastinal lymph node metastasiscan occur in patients with supraclavicularnodal metastasis. Because of the high incidence ofcervical nodal metastasis, the entire neck includingthe retropharyngeal nodes and Level I–V lymphnodes are considered at risk for involvement. Forthis reason, all these nodal regions are to be includedin the clinical target volume for radiation therapy.However, results from a number of recently reportedseries questioned the necessity of encompassing thelower neck in patients with no cervical adenopathy,as nodal spread usually occurs in an orderly fashion(Gao et al. 2009; Tang et al. 2009). Table 4.2 summarizesthe distribution of metastatic nodes basedon MRI ± 18-fluorodeoxyglucose positron-emissiontomography ( 18 FDG PET).Table 4.2. Distribution of metastatic nodes in NPCNodal sites4.5.4Distant SpreadDistant metastasis occurs in 3% of the cases at presentationand may occur in a much higher percentage(ranging from 18% to above 50%) of the cases inthe disease course (Ahmad and Stefani 1986;Bedwinek et al. 1980; Chu et al. 1984; Hoppe et al.1976; Lee and Fu 2004; Moench and Phillips 1972).The incidence of distant metastases correlate withthe presence of advanced nodal metastasis, especiallyin the supraclavicular region (Lee et al. 1996a, b; Teoet al. 1991a,b, 1992). The skeleton is the most commonsite of distant metastasis. Other common sitesof metastases include the lungs and the liver.4.6DiagnosisPercentage (NGet al. 2004) aRetropharyngeal nodes 82 86.4Level I nodesa:–b:2.2 c a:0b:3.1Level II nodes 95.5 a:42.7b:65Level III nodes 60.7 28.8Level IV nodes 34.8 7.1Level V nodes 27 11.1Supraclavicular nodes 22.5 3.9Level VI nodes 2.2 –Level VII nodes 1.1 –Parotid nodes 3.4 –Mediastinal nodes 4.5 –Abdominal nodes 3.4 –Retrostyloid nodes – 0Percentage (MAOet al. 2008) baStudy was done based on the findings on MRI and 18 FDG PETof 101 patientsbStudy was done based on the findings on MRI of 924 patientscDesignated as submandibular nodes in the studySince the stage of disease is the most importantdeterminant of prognosis in NPC, a delay in diagnosiscan be detrimental to the patient in terms of local