Neck dissection classification: nodal levels, AAO-HNS/AHNS terminology and clinical evidence

Key points

• The neck is divided into levels I–VI; sublevels IA/IB, IIA/IIB and VA/VB form the standard language for surgical and radiological communication.
• The AHNS and AAO-HNS classification defines four categories: radical, modified radical, selective and extended neck dissection; selective dissection is written with the levels removed, e.g. SND (I–III).
• D'Cruz et al. (NEJM 2015) showed that elective neck dissection gave higher overall and disease-free survival than observation with therapeutic dissection on relapse in lateralised T1–T2 oral squamous cell carcinoma.
• In selected early oral cavity cancers, sentinel lymph node biopsy can be an alternative to elective dissection in experienced centres.

Cervical nodal levels and boundaries

• IA (submental): the triangle between the anterior bellies of both digastric muscles and the hyoid bone.
• IB (submandibular): the body of the mandible above, the anterior belly of the digastric in front and the stylohyoid muscle behind; on imaging, the posterior edge of the submandibular gland is used as the I/II boundary.
• II (upper jugular): from the skull base to the level of the hyoid; the stylohyoid muscle (radiologically the posterior edge of the submandibular gland) in front and the posterior border of the sternocleidomastoid (SCM) behind. The spinal accessory nerve divides it into IIA (anterior to the nerve) and IIB (posterior to the nerve).
• III (middle jugular): between the hyoid and the lower border of the cricoid cartilage; the sternohyoid muscle in front and the posterior border of the SCM behind.
• IV (lower jugular): between the lower border of the cricoid and the clavicle; anterior and posterior boundaries as for level III.
• V (posterior triangle): the posterior border of the SCM in front and the trapezius behind; a horizontal plane at the lower border of the cricoid divides it into VA (upper) and VB (lower).
• VI (anterior/central compartment): the hyoid above, the suprasternal notch below and the common carotid arteries laterally.
• VII (superior mediastinum): the superior mediastinal nodes below the suprasternal notch are called level VII in some systems (e.g. AJCC); the 2008 consensus specifically addressed the terminology of these nodes.

AAO-HNS/AHNS classification (Robbins et al. 2002, 2008)

The 2002 update was proposed by the American Head and Neck Society (AHNS) and the AAO-HNS; the 2008 consensus revised the boundaries between levels I and II and between III/IV and VI, the terminology of the superior mediastinal nodes and the method of submitting surgical specimens for pathology.

• Radical neck dissection (RND): removal of levels I–V together with the SCM, internal jugular vein (IJV) and spinal accessory nerve.
• Modified radical neck dissection (MRND): levels I–V are removed but one or more of these three non-lymphatic structures is preserved; the preserved structure should be named.
• Selective neck dissection (SND): one or more of the levels routinely removed in RND is preserved. Clinical examples: SND (I–III) for the oral cavity (formerly supraomohyoid), SND (II–IV) for the larynx, oropharynx and hypopharynx, SND (II–V) for skin cancers behind the ear and central dissection (VI) for thyroid cancer.
• Extended neck dissection: the addition of further lymphatic groups (e.g. retropharyngeal, parotid, superior mediastinal) or non-lymphatic structures (e.g. hypoglossal nerve, carotid artery, skin) to a standard dissection.

Nomenclature proposed by Ferlito et al. (2011)

Published on behalf of the International Head and Neck Scientific Group, this proposal argues for writing out what was removed instead of using category names: the abbreviation "ND" is followed in parentheses by the levels and sublevels removed and then by the non-lymphatic structures removed. Examples:

• ND (I–V, SCM, IJV, CN XI) = classic radical neck dissection.
• ND (I–V, SCM, IJV) = modified radical dissection preserving the spinal accessory nerve.
• ND (I–V, SCM, IJV, CN XI, CN XII) = extended dissection including the hypoglossal nerve.
• ND (II–IV) = SND (II–IV); a procedure such as ND (II–IV, SCM) has no direct equivalent in the 2008 classification.

Whichever system is used, the operative note and pathology request should state the side, the levels and sublevels removed and the structures preserved or resected.

Elective versus therapeutic neck dissection

Therapeutic dissection is performed for a clinically or radiologically positive neck. Elective dissection is considered for the clinically N0 neck when the risk of occult metastasis is high; in the oral cavity this risk rises with depth of invasion.

In the randomised trial by D'Cruz et al., funded by Tata Memorial Centre (2004–2014, 596 patients; first 500 reported, median follow-up 39 months), ipsilateral elective dissection at the time of primary surgery was compared with observation and therapeutic dissection on nodal relapse in lateralised T1–T2 oral squamous cell carcinoma. Three-year overall survival was 80.0% versus 67.5% (hazard ratio for death 0.64) and disease-free survival 69.5% versus 45.9%, favouring the elective arm.

Sentinel lymph node biopsy

In the randomised non-inferiority trial by Hasegawa et al. across 16 Japanese centres (JCO 2021), sentinel node–navigated neck dissection was compared with standard selective dissection in T1–T2 N0 oral cavity squamous cell carcinoma (depth of invasion ≥4 mm for T1). Three-year overall survival was non-inferior at 87.9% versus 86.6%, and neck function scores were better in the sentinel arm.

NICE NG36 likewise recommends sentinel lymph node biopsy instead of elective dissection in T1–T2 N0 oral cavity cancer unless cervical access (e.g. for a free flap) is needed. The technique requires nuclear medicine, pathology resources such as serial sectioning and immunohistochemistry, and experience; the possibility of false-negative results should be discussed with the patient.

Spinal accessory nerve and shoulder morbidity

Even when the spinal accessory nerve is preserved, traction and devascularisation during level IIB and V dissection can cause trapezius dysfunction with shoulder pain, limited abduction and scapular droop. Preserving IIB where oncologically appropriate has been reported to reduce the risk of nerve dysfunction. NICE recommends considering progressive resistance training as soon as possible after neck dissection for people with impaired shoulder function.

Implications for practice

Shared terminology reduces error between the radiology report, operative note, pathology and radiotherapy planning. Neck management in early oral cavity cancer (elective dissection, sentinel biopsy or, in selected cases, observation) should be decided in a multidisciplinary tumour board, taking into account primary tumour features, reconstruction needs, local resources and patient preference.

Limitations and currency

The Ferlito et al. nomenclature is a proposal and is used in practice alongside the 2002/2008 classification. The populations and staging systems (TNM 7) of the D'Cruz and Hasegawa trials may differ from current practice. This summary was prepared as of November 2026; current versions of guidelines such as NCCN and NICE should be checked.