Neck Node Levels and Their Anatomical Boundaries
The neck is divided into specific lymph node levels with well-defined anatomical boundaries that are essential for standardized classification in head and neck cancer staging and management. 1, 2
Level I (Submental and Submandibular Group)
- Level IA (Submental): Bounded by the anterior belly of digastric muscles laterally, hyoid bone inferiorly, and mandibular symphysis superiorly 2
- Level IB (Submandibular): Contains nodes within the submandibular triangle bounded by the anterior and posterior bellies of the digastric muscle and the inferior border of the mandible 2, 3
Level II (Upper Jugular Group)
- Level IIA: Nodes located anterior to the spinal accessory nerve, extending from the skull base superiorly to the inferior border of the hyoid bone 2, 3
- Level IIB: Nodes located posterior to the spinal accessory nerve, from the skull base to the inferior border of the hyoid bone 2, 3
- Both sublevels are bounded laterally by the posterior border of the sternocleidomastoid muscle and medially by the lateral border of the stylohyoid muscle 2
Level III (Middle Jugular Group)
- Extends from the inferior border of the hyoid bone superiorly to the inferior border of the cricoid cartilage 2
- Bounded laterally by the posterior border of the sternocleidomastoid muscle and medially by the lateral border of the sternohyoid muscle 2, 1
Level IV (Lower Jugular Group)
- Extends from the inferior border of the cricoid cartilage superiorly to the clavicle inferiorly 2
- Bounded laterally by the posterior border of the sternocleidomastoid muscle and medially by the lateral border of the sternohyoid muscle 2, 1
Level V (Posterior Triangle Group)
- Level VA: Extends from the apex of the convergence of the sternocleidomastoid and trapezius muscles superiorly to the inferior border of the cricoid cartilage 4
- Level VB: Extends from the inferior border of the cricoid cartilage to the clavicle 4
- Some authors further subdivide Level VA into Level VAs (superior) and Level VAi (inferior), separated by the lower two-thirds of the spinal accessory nerve 4
- Bounded anteriorly by the posterior border of the sternocleidomastoid muscle and posteriorly by the anterior border of the trapezius muscle 2, 4
Level VI (Central Compartment Group)
- Extends from the hyoid bone superiorly to the suprasternal notch inferiorly 5
- Bounded laterally by the medial borders of the carotid sheaths and posteriorly by the prevertebral fascia 5
- Level VIa: Includes prelaryngeal, intercricothyroidal, pretracheal, and perithyroidal nodes 5
- Level VIb: Encompasses inferior laryngeal nodes 5
Level VII (Superior Mediastinal Group)
- Extends from the suprasternal notch superiorly into the superior mediastinum 5
- Should not be confused with Level VI nodes 5
Clinical Significance in Head and Neck Cancer
- The type of neck dissection (comprehensive or selective) is determined based on the clinical staging and primary tumor location 1
- For N0 disease, selective neck dissection typically includes:
- For N1-N2 disease, selective or comprehensive neck dissection may be performed 1
- For N3 disease, comprehensive neck dissection is recommended 1
Imaging Characteristics of Lymph Nodes
- On imaging, suspicious features of lymph nodes include:
- Most masses greater than 3 cm in diameter typically represent confluent nodes or tumor in soft tissues rather than single lymph nodes 1
Important Considerations
- Histologic examination of a selective neck dissection specimen typically includes 6 or more lymph nodes 1
- Radical or modified radical neck dissection specimens usually include 10 or more lymph nodes 1
- Level II (upper deep cervical) nodes are the most commonly involved nodes across all primary sites, comprising approximately 69% of all neck node metastases 7
- The level of nodal involvement has prognostic significance - as the level of nodes falls from submandibular to supraclavicular region, the prognosis worsens 7