**3. Staging and classification**

During the last 20 years, NPC natural history became more known in term of loco-regional extension as well as metastatic disease with technical improvements of flexible nasofibroscopes and modern imagery, such as magnetic resonance imagery and Petscan(Chan et al,2011). This better definition of loco-regional disease extension leads to successive actualizations (1997, 2002 then 2009), of the more used TNM UICC anatomoclinical classification, more adapted to discriminate between the different T and N prognostic stages and eventually to adjust therapeutic protocols according to risk group (Union for International Cancer Control,2009).

T1 Nasopharynx, oropharynx or nasal cavity (**was T2a\***) without parapharyngeal extension

T2 Parapharyngeal extension (**was T2b\***)

T2a Tumour extends to oropharynx and/or nasal cavity without parapharyngeal extension

T2b Tumour with parapharyngeal extension

T3 Bony structures of skull base and/or paranasal sinuses

T4 Intracranial, cranial nerves, hypopharynx, orbit, infratemporal fossa/masticator space

N1 Unilateral **cervical**, unilateral or bilateral retropharyngeal lymph nodes, above supraclavicular fossa; < 6 cm

N2 Bilateral **cervical** above supraclavicular fossa; < 6 cm

N3 Metastasis in lymph node(s), >6 cm in dimension (N3a) or in the supraclavicular fossa (N3b)>6 cm

7th TNM classification of UICC (International Union against Cancer, 2009)-AJCC, American Joint Committee on Cancer. \*Recent modification
