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Commentary
July 2002

Classification and Terminology of Neck Dissection

Arch Otolaryngol Head Neck Surg. 2002;128(7):747-748. doi:10.1001/archotol.128.7.747

A NOTEWORTHY article by Robbins et al1 in this issue of the ARCHIVES describes an update of the original classification of neck dissection published in 19912 and proposed by the Committee for Head and Neck Surgery and Oncology of the American Academy of Otolaryngology–Head and Neck Surgery (AAO-HNS). Recognizing the need to standardize the expanding terminology on neck dissection procedures, the Committee has defined the anatomical boundaries for lymph node dissection and recommended principles on which the terminology for neck dissection surgical procedures should be based.

The updated classification represents a consensus among representative head and neck surgeons of the American Head and Neck Society and the AAO-HNS and does not differ substantially from the recommendations of the AAO-HNS's Committee on Neck Dissection a decade ago. The 2 most significant changes concern the way in which various selective neck dissections are described (each variant is depicted by "SND" and the use of brackets to denote the levels or sublevels removed) and the use of radiologically depicted anatomical structures to define boundaries between various neck levels and sublevels to designate imaged nodes accurately. The Committee was composed of distinguished authorities of international standing and vast experience of the diagnostic, clinical, therapeutic, and prognostic problems of head and neck cancer. It was chaired by K. Thomas Robbins and included a radiologist, Peter Som, from the Department of Radiology, Mount Sinai School of Medicine, City University, New York, NY, who had worked in our specialty to define parameters for accurately describing the orientation of lymph nodes in the neck in relation to the level system.3,4 The revised operative classification adopts several imaging-based landmarks, ie, the bottom of the hyoid will separate level II and III nodes, the bottom of the cricoid cartilage will separate levels III and IV, and the back of the submandibular gland will separate levels I and II. This brings the clinical and imaging classifications closer together.

The Committee opted to further divide some neck levels into sublevels. This is very useful in distinguishing level I as levels IA (submental lymph nodes) and IB (submandibular lymph nodes). Since many tumors of the head and neck do not metastasize to level IA,5,6 level IA dissection is not indicated, particularly in the absence of metastases to other neck levels. Conversely, the frequency of involvement of level IA nodes justifies extirpation of this region in neck dissection for primary tumors of the anterior or lateral floor of the mouth, anterior third of the tongue, anterior mandibular alveolar ridge, and anterior lower gingiva. Dissection of level IA is also indicated for cancers of the lower lip, chin, cheek, and skin of the nose. Cancers of the upper lip and maxillary sinus rarely metastasize to the submental triangle.6 It is also important to distinguish level II as levels IIA and IIB. In 2002, Köybasioglu et al7 found no positive nodes in level IIB (the supraretrospinal recess) in patients with laryngeal cancer and N0 necks treated with lateral selective neck dissection, and in N1 and N2 necks treated with radical neck dissection and modified radical neck dissection. Separating level V into level VA (spinal accessory nodes) and level VB (transverse cervical and supraclavicular nodes) permits a distinction between lymph node involvement of the transverse cervical nodal chain and lymphadenopathy associated with the lower two thirds of the spinal accessory nerve.8 These considerations are all good reasons for promoting an educational process for separating these levels into A and B. Levels III, IV, and VI are not subdivided.

This revised classification has accepted 6 levels of cervical lymph nodes, whereas the Memorial Sloan-Kettering Cancer Center classification,9 the American Joint Committee on Cancer,10 and Som et al3 recommended designating the superior mediastinal nodes as level VII.11 Robbins12 points out that the superior mediastinal nodes lie outside the neck area and we should resist the temptation to label adjacent lymph node groups as new levels. Lymph nodes involving regions that are not located within the 6 levels should be designated by the name of their specific nodal group (ie, retropharyngeal lymph nodes, suboccipital lymph nodes, postauricular lymph nodes, etc). Noncervical lymph node metastases from head and neck cancer have been reported in the literature and must be classified as distant metastases according to the International Union Against Cancer13; mediastinal and axillary metastases may represent a contiguous regional dissemination of the disease, however.14 The definition of the types of neck dissection remains as previously outlined in the 1991 classification report,2 which enjoys general international acceptance. These are (1) radical neck dissection, considered the standard basic procedure for cervical lymphadenectomy, while all other procedures represent 1 or more modifications of this procedure; (2) modified radical neck dissection, which preserves 1 or more nonlymphatic structures (ie, spinal accessory nerve, internal jugular vein, and sternocleidomastoid muscle) routinely removed in radical neck dissection; (3) selective neck dissection, which preserves 1 or more lymph node groups/levels routinely removed in radical neck dissection; and (4) extended neck dissection, when additional lymph node groups or nonlymphatic structures are removed with respect to radical neck dissection. Radical neck dissection includes the removal of all ipsilateral cervical lymph node groups extending from the inferior border of the mandible above to the clavicle below, and from the lateral border of the sternohyoid muscle, the hyoid bone, and the contralateral anterior belly of the digastric muscle medially to the anterior border of the trapezius muscle posteriorly. It includes all lymph node groups from levels I to V (the submental, submandibular, upper jugular, middle jugular, lower jugular, and posterior triangle groups). The spinal accessory nerve, the internal jugular vein, the sternocleidomastoid muscle, the submandibular gland, the tail of parotid gland, and the cervical plexus nerves are all removed. Modified radical neck dissection has been subclassified by some as types I, II, and III. The American Head and Neck Society/AAO-HNS Committee discourages the use of numerals to identify variations among these procedures, because numerical designations can lead to confusion. The structure(s) preserved should be specifically named, eg, "modified radical neck dissection with preservation of the spinal accessory nerve."

Many terms have been used in the past to indicate different neck dissections and they are often confusing, nondescriptive, and a hindrance to interinstitutional communication.15 To prevent misinterpretations, overlaps, and lack of standardization among head and neck oncologists, I would recommend that all neck dissections be described by specifying the levels dissected and the relevant nonlymphatic structures preserved or removed,16 as proposed by the American Head and Neck Society for selective neck dissection in its update on neck dissection classification.1

References
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