Robbins 2002 - JAMA Otolaryngology - Neck Dissection Classification Update
Jing Qin Tay
10/6/2023
Summary
This article presents revisions to the classification system for neck dissection procedures proposed by the American Head and Neck Society and the American Academy of Otolaryngology-Head and Neck Surgery. The original classification system was published in 1991 and has been widely adopted. However, advances in understanding of lymph node metastasis patterns and refinements in surgical techniques warranted an update.
Types of neck dissection:
Radical neck dissection: Removal of lymph nodes from levels I-V, as well as spinal accessory nerve, internal jugular vein, and sternocleidomastoid muscle.
Modified radical neck dissection: Radical dissection sparing one or more non-lymphatic structures (accessory nerve, vein, muscle).
Selective neck dissection (SND): Removal of lymph node groups at highest risk for metastasis based on primary tumor location. Denoted by levels/sublevels in parentheses, e.g. SND (I-III).
SND for oral cavity cancer: SND (I-III) removing submental, submandibular, and jugular nodes. SND (I-IV) also advocated for oral tongue cancers.
SND for oropharynx/larynx/hypopharynx cancers: SND (II-IV) removing upper, middle, and lower jugular nodes.
SND for thyroid cancer: SND (VI) removes central compartment (pretracheal, paratracheal, prelaryngeal) nodes.
Extended neck dissection: Removal of additional nodes or non-lymphatic structures not included in radical dissection, e.g. retropharyngeal nodes.
The main updates are:
Introduction of sublevels within the 6 neck levels to distinguish lymph node groups that may have distinct biological significance. The sublevels are IA, IB, IIA, IIB, VA, and VB.
More precise definition of the anatomical boundaries between neck levels, using radiologic landmarks that correlate with the surgical levels. Key differences from the 1991 system are using the hyoid bone to differentiate levels II and III, and the cricoid cartilage to differentiate levels III and IV.
Elimination of named selective neck dissections (e.g. supraomohyoid), instead using a notation system denoting the levels and sublevels removed. The rationale is the increasing variations in selective dissections, making named dissections inaccurate.
Emphasis on tailoring neck dissections based on predictable nodal metastasis patterns from the primary tumor site. Selective removal of only at-risk levels and sublevels is advocated when appropriate.
Addition of suboccipital, retropharyngeal, paratracheal and superior mediastinal nodes as potential targets for removal in extended neck dissections when indicated by the primary tumor location.
Overall, the updated system allows more precise communication between clinicians regarding extent of lymph node removal. It reinforces selective neck dissection guided by likely nodal spread patterns. The revisions also align neck levels with radiologic landmarks to improve correlation. By eliminating named selective dissection types, the system can accommodate the increasing surgical variations utilized today while maintaining a simple framework. The authors note this update represents continued evolution in understanding and techniques, with future revisions likely needed.
On sublevels:
Sublevel IA contains submental lymph nodes bounded by the anterior bellies of the digastric muscles and the hyoid bone. At risk from cancers of the oral floor, anterior tongue, lower lip.
Sublevel IB contains submandibular nodes bounded by the digastric muscle, stylohyoid muscle and mandible body. At risk from oral cavity, nasal, midface cancers.
Sublevels IIA and IIB split the upper jugular nodes. IIA is medial, IIB lateral to the spinal accessory nerve. IIB has higher risk for metastases from oropharynx cancers.
Sublevels VA contains spinal accessory nodes, VB contains transverse cervical and supraclavicular nodes below the cricoid cartilage. VB nodes carry worse prognosis if positive.
On anatomical boundaries:
Level I revised to all nodes between hyoid bone and mylohyoid muscle on imaging. Sublevels IA and IB further divide it.
Levels II and III now divided by hyoid bone rather than carotid bifurcation.
Levels III and IV now divided by cricoid cartilage rather than omohyoid muscle.
On selective neck dissections:
For oral cavity cancer, SND (I-III) is standard. SND (I-IV) advocated for oral tongue cancer due to risk of level IV metastases.
For oropharynx/larynx/hypopharynx cancer, SND (II-IV) is standard. IIB may be omitted for larynx/hypopharynx.
For thyroid cancer, SND (VI) removes central compartment nodes. Can add II-V and superior mediastinal nodes if required.
For cutaneous cancers, posterior scalp/neck requires SND (II-V) plus postauricular and suboccipital nodes.
Extended neck dissections added for parapharyngeal, retropharyngeal, perifacial and other nodes not in radical neck dissection.