Table 1.

TNM classification of NPC (http://headandneckcancer.org).

		Characteristics
T Stage	T1	The tumour is within the nasopharynx, or it has grown into the oropharynx and/or nasal cavity, but no extension into the parapharyngeal space (soft tissue space behind and to the side of the pharynx).
	T2	The tumour extends into the parapharyngeal space.
	T3	The tumour has grown into the bone of the skull base and/or the sinuses.
	T4	The tumour has grown into the skull and/or involves the cranial nerves, hypopharynx and eye socket. Alternatively, it has extended to the infratemporal fossa or masticator space.
N Stage	N0	No evidence of cancer spread to LNs 1 in the neck or retropharyngeal space.
	N1	Presence of cancer in the LNs on one side of the neck (6 cm or less in size) and above the clavicle (supraclavicular fossa). The LNs at this stage should be found in the retropharyngeal space (6 cm or less in size, one side or both).
	N2	Presence of cancer in the LNs on both sides of the neck (biggest LN is 6 cm or less) and above the supraclavicular fossa.
	N3a	Presence of a LN with cancer bigger than 6 cm.
	N3b	Presence of a LN of any size that is far down the neck, just above the clavicle.
M Stage	M0	No evidence of distant spread outside the head and neck.
	M1	Evidence of spread outside the head and neck.

¹ LNs, Lymph Nodes.