There are approximately 300 lymph nodes in the neck, and they can be classified in a number of different ways.
History The classification of the cervical lymph nodes is generally attributed to
Henri Rouvière in his 1932 publication "Anatomie des Lymphatiques de l'Homme" Rouviere described the cervical lymph nodes as a collar which surrounded the
upper aerodigestive tract, consisting of submental, facial, submandibular, parotid, mastoid, occipital and retropharyngeal nodes, together with two chains that run in the long axis of the neck, the anterior cervical and postero-lateral cervical groups. However, this system was based upon anatomical landmarks found in dissection, making it imperfectly suited to the needs of clinicians, which led to new terminology for the lymph nodes that could be palpated. The most commonly used system is one based on a classification of the lymph nodes into numbered groupings, devised at the
Memorial Sloan Kettering Cancer Center in the 1930s. This has been variously modified since. In 1991, the
American Academy of Otolaryngology published a standardised version of thisto provide a uniform approach to
neck dissection that was updated in 2002, including the addition of sub-levels, e.g. IIA and IIB.
Modern systems More recently, classification systems have been proposed organized around what can be observed via diagnostic imaging. In addition to the American Academy of Otolaryngology, systems have been devised by the
American Joint Committee on Cancer (AJCC). The AJCC system from the 7th edition of the Staging Manual (2009) remains unchanged in the 8th edition of 2018.
Lymph node levels The American Academy of Otolaryngology system (2002) divides the nodes as follows: • Level I:
Submental and
submandibular nodes • Level Ia:
Submental - these are below the
mentum of the chin more anteriorly between a triangle formed by the anterior belly of the
digastric muscles on each side, and with the
hyoid as its base in the
axial plane. • Level Ib:
Submandibular triangle - posterolateral to the anterior belly of the digastric muscle between the area formed by its margin, the
stylohyoid muscle and the body of the
mandible. • Level II:
Upper jugular nodes (Subdigastric nodes) - upper third of the
internal jugular vein and adjacent
accessory nerve. The upper boundary is the
base of the skull and the lower boundary is the hyoid. The anteromedial boundary is the
stylohyoid muscle extending between the styloid and hyoid bones, and the posterolateral boundary is the
sternocleidomastoid muscle. • Level IIa: Anteromedial to the vertical plane of the accessory nerve. This nerve is not seen on
CT, but correlates to the posterior edge of the internal jugular vein and below the
lateral mass of the atlas at the skull base but above the hyoid. • Level IIb:
Deep to the jugular vein and
below the lateral mass of the skull base, with its lower margin being the hyoid. • Level III:
Middle jugular nodes - middle third of the internal jugular vein, between the hyoid and
cricoid cartilage. They are bounded medially by the
sternohyoid muscle and are deep to the sternocleidomastoid muscle. They are also lateral to the
internal or
common carotid arteries; nodes medial to these vessels are in the anterior compartment of level VI. • Level IV:
Lower jugular nodes - lower third of the internal jugular vein between the cricoid and
clavicle, lateral to the sternohyoid and anteromedial to an
oblique line drawn between the posterior sternocleidomastoid at the lateral neck and
anterior scalene muscle more posteromedially. Similar to level III, level IV nodes are also lateral to the carotid, with nodes medial to this being level VI as well. • Level V:
Posterior triangle nodes - nodes posterolateral to the sternocleidomastoid and anteromedial to the trapezius above the clavicle. The nodes are around the lower half of the spinal accessory nerve and the
transverse cervical artery, and include the
supraclavicular nodes. • Level VA: Above the horizontal plane formed by the inferior border of the
anterior cricoid arch, including the spinal accessory nodes. • Level VB: Lymph nodes below this plane, including the transverse cervical nodes and supraclavicular nodes (except
Virchow's node which is in IV). • Level VI: Anterior compartment nodes -
Pretracheal,
paratracheal,
precricoid (Delphian) and perithyroid nodes, including those on the
recurrent laryngeal nerve. The upper border is the hyoid, the lower the
suprasternal notch, and the lateral borders the
common carotid arteries. The American Joint Committee on Cancer (AJCC) system differs from the above by including Level VII, but the American Academy considered these to be anatomically
mediastinal rather than cervical nodes, and therefore should not be included in the classification of neck nodes. However it is based on the 2002 American Academy system, although the boundaries are defined slightly differently. The boundaries are defined as (Superior, Inferior, Antero-medial, Postero-lateral) • Level IA: Symphysis of mandible, Body of hyoid, Anterior belly of contralateral digastric muscle, Anterior belly of ipsilateral digastric muscle • Level IB: Body of mandible, Posterior belly of digastric muscle, Anterior belly of digastric muscle, Stylohyoid muscle • Level IIA: Skull base, Horizontal plane defined by the inferior border of the hyoid bone, The stylohyoid muscle, Vertical plane defined by the spinal accessory nerve • Level IIB: Skull base, Horizontal plane defined by the inferior body of the hyoid bone, Vertical plane defined by the spinal accessory nerve, Lateral border of the sternocleidomastoid muscle • Level III: Horizontal plane defined by the inferior body of hyoid, Horizontal plane defined by the inferior border of the cricoid cartilage, Lateral border of the sternohyoid muscle, Lateral border of the sternocleidomastoid or sensory branches of
cervical plexus • Level IV: Horizontal plane defined by the inferior border of the cricoid cartilage, Clavicle, Lateral border of the sternohyoid muscle, Lateral border of the sternocleidomastoid or sensory branches of cervical plexus • Level VA: Apex of the convergence of the sternocleidomastoid and trapezius muscles, Horizontal plane defined by the lower border of the cricoid cartilage, Posterior border of the sternocleidomastoid muscle or sensory branches of cervical plexus, Anterior border of the trapezius muscle • Level VB: Horizontal plane defined by the lower border of the cricoid cartilage, Clavicle, Posterior border of the sternocleidomastoid muscle, Anterior border of the trapezius muscle • Level VI: Hyoid bone, Suprasternal notch, Common carotid artery, Common carotid artery • Level VII: Suprasternal notch,
Innominate artery,
Sternum,
Trachea,
esophagus, and
prevertebral fascia While an imaging based system was proposed in 1999, these concepts were integrated into the 2002 revision of the American Academy system. In addition to needing a standardised approach to classification of lymph nodes for the purposes of neck dissection, the application of
radiation therapy also requires such an approach and has resulted in an international consensus guideline (2013). ==Clinical significance==