Level III Lymph Nodes on Neck Ultrasound
Level III lymph nodes are located in the mid-jugular region of the neck, positioned along the internal jugular vein between the hyoid bone superiorly and the cricoid cartilage (or omohyoid muscle) inferiorly. 1
Anatomical Boundaries
Level III nodes are part of the standardized six-level classification system (Levels I-VI) used universally for surgical planning and oncological evaluation in head and neck cancer. 2, 3 The specific anatomical landmarks include:
- Superior boundary: Inferior border of the hyoid bone or horizontal plane where the carotid bifurcation crosses the internal jugular vein 4
- Inferior boundary: Inferior border of the cricoid cartilage or the omohyoid muscle 1, 4
- Medial boundary: Medial edge of the sternohyoid muscle 4
- Lateral boundary: Lateral edge of the sternocleidomastoid muscle or sensory branches of cervical plexus 4
- Anterior boundary: Lateral edge of the sternohyoid muscle 4
- Posterior boundary: Posterior border of the sternocleidomastoid muscle 4
These nodes are positioned along the internal jugular vein in the mid-neck region, typically found close to the vessel's medial edge or directly adjacent to it. 1, 5
Clinical Significance
Level III nodes receive lymphatic drainage primarily from:
- Oral cavity primaries (lip and oral cavity tumors commonly metastasize to levels I-III) 1
- Oropharyngeal, hypopharyngeal, and laryngeal primaries (which typically spread to levels II-IV) 1
- Skin cancers of the head and neck (can metastasize to levels I-V) 1
For surgical planning, selective neck dissection for oral cavity N0 disease typically includes at least levels I-III, while oropharyngeal tumors require levels II-IV. 1, 2
Imaging Features of Suspicious Level III Nodes
On ultrasound and cross-sectional imaging, pathologic features to identify include:
- Size: Nodes greater than 1.5 cm are considered suspicious 2, 3
- Shape: Rounded rather than oval configuration 1, 2
- Internal architecture: Loss of fatty hilum, heterogeneous internal structure, or necrotic centers 1, 2, 3
- Borders: Irregular borders or evidence of extracapsular extension 1, 2
A critical pitfall to avoid is using vague terminology like "mid-neck nodes" without specifying the level classification, as precise documentation of Level III involvement directly impacts surgical planning and treatment decisions. 5