Table 1.

Simplified numerical classification system

Level	Location
IA	Submental lymph nodes
IB	Submandibular lymph nodes
II	Internal jugular (deep cervical) chain from the base of the skull to the inferior border of the hyoid bone
III	Internal jugular (deep cervical) chain from the hyoid bone to the inferior border of the cricoid arch
IV	Internal jugular (deep cervical) chain between the inferior border of the cricoid arch and the supraclavicular fossa
V	Posterior triangle or spinal accessory nodes
VI	Central compartment nodes from the hyoid bone to the suprasternal notch
VII	Nodes inferior to the suprasternal notch in the upper mediastinum