NECK LEVELS.pdf

Neck Dissection Classification Update

Revisions Proposed by the American Head and Neck Society andthe American Academy of Otolaryngology–Head and Neck Surgery

K. Thomas Robbins, MD; Garry Clayman, MD; Paul A. Levine, MD; Jesus Medina, MD; Roy Sessions, MD;Ashok Shaha, MD; Peter Som, MD; Gregory T. Wolf, MD; and the Committee for Head and Neck Surgery and Oncology,American Academy of Otolaryngology–Head and Neck Surgery

S ince the first description of the radical neck dissection by George Crile almost a centuryago, many variations and modifications of the procedure have been added. These in-clude the functional neck dissection, the modified radical neck dissection, and variousselective neck dissections. In response to the need for an organized approach in describ-

ing these operations, the Committee for Head and Neck Surgery and Oncology of the AmericanAcademy of Otolaryngology–Head and Neck Surgery (AAO-HNS) in 1988 initiated an effort todevelop a standardized classification system for neck dissection (Table 1). During this process,input was obtained from the Education Committee of the American Society for Head and NeckSurgery (ASHNS) and its Council. The final product, endorsed by the ASHNS and the AAO-HNS,was published in the ARCHIVES1 and as a monograph2 by the AAO-HNS in 1991.

In 1998, 10 years following the initiationof the neck dissection classification project,an ad hoc committee of the newly formedAmerican Head and Neck Society (AHNS)was convened to review the original clas-sification scheme. This was prompted bythe AAO-HNS’s desire to update its mono-graph on the subject and include the re-cent revisions to the American Joint Com-mission on Cancer (AJCC) staging systemfor head and neck cancer. However, therewas also a need to consider revisions to theneck dissection classification in light ofnew observations regarding the biologi-cal function of lymph node metastases,further refinements in selective neck dis-section procedures, as well as a need toredefine the anatomical boundaries ofcertain neck levels and be consistent withthe anatomical boundaries used in radio-logic studies of the neck.

Chairedbytheprimaryauthor(K.T.R.),the Committee for Neck Dissection Class-

ification of the AHNS met several timesover a 2-year interval to complete itswork. Representation on the committeealso included a radiologist, (P. S.), whohad worked within his own specialty todefine parameters by which the orienta-tion of lymph nodes in the neck could beaccurately described in relation to thelevel system.3,4 During this interval, themembers serving at that time on the Acad-emy’s Committee for Head and NeckSurgery and Oncology provided addi-tional advice.

As the committee members re-viewed the 1991 neck dissection classifi-cation system (Table 1),1 there was a gen-eral consensus that the basic approachpreviously followed had clearly achievedits original objective to standardize neckdissection terminology using a system thatwas logical, straightforward, and easy toremember. In fact, the committee mem-bers noted that the worldwide use of thesystem was a testimony to its practicalityand usefulness. Consequently, a strong de-sire was expressed to maintain this struc-ture because any radical alterations car-ried a risk of losing the widespread supportfor a standardized neck dissection classi-fication. However, it was also believedthere was an opportunity to introduce cer-

From the University of Florida, Gainesville (Dr Robbins); the M. D. Anderson CancerCenter, Houston, Tex (Dr Clayman); the University of Virginia, Charlottesville(Dr Lavine); the University of Oklahoma, Oklahoma City (Dr Medina); the Beth IsraelHospital, New York, NY (Dr Sessions); the Memorial Sloan Kettering Cancer Institute,New York (Dr Shaha); the Mt Sinai Medical Center, New York (Dr Som); and theUniversity of Michigan, Ann Arbor (Dr Wolf). Committee members are listed in a boxon page 758.

ORIGINAL ARTICLE

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tain modifications that would allow the original classi-fication to remain contemporary and in keeping withthe current philosophy for managing lymph nodemetastases.

DIVISION OF LYMPH NODES BY LEVELS

The committee supported the continued use of the levelsystem to delineate the location of lymph node diseasein the neck (Figure 1).5 The level system is well knownand easy to remember and now serves as the basis for de-scribing various selective neck dissections. Contrary tothe recommendations by others, it did not recommendincluding additional levels such as level VII for the su-perior mediastinum. It was believed that the 6 levels cur-rently used encompassed the complete topographicanatomy of the neck. Lymph nodes involving regions notlocated within this region would be referred to by the nameof their specific nodal group. In addition to the superiormediastinum, other examples include the retropharyn-geal lymph nodes, the periparotid lymph nodes, the buc-cinator nodes, and the postauricular and suboccipitalnodes. Figure 1 depicts the topographical boundaries ofthe level system.

DIVISION OF NECK LEVELS BY SUBLEVELS

The committee decided to introduce the concept of sub-levels into the classification, since certain zones havebeen identified within the 6 levels, some of which mayhave biological significance independent of the largerzone in which they lie. These are outlined in Figure 2as sublevels IA (submental nodes), IB (submandibularnodes), IIA and IIB (together comprising the upperjugular nodes), and VA (spinal accessory nodes) and VB(transverse cervical and supraclavicular nodes). Theboundaries for each of these sublevels are specified inTable 2.

The risk of nodal disease in sublevel IIB is greaterfor tumors arising in the oropharynx compared with theoral cavity and larynx. Thus, in the absence of clinicalnodal disease in sublevel IIA, it is likely not necessary toinclude sublevel IIB for tumors arising in these lattersites. The dissection of the node-bearing tissue of sub-level IIB (submuscular recess) is not without an in-creased risk of morbidity. Adequate exposure necessi-tates significant manipulation of the spinal accessorynerve (SAN) and may account for trapezius muscledysfunction observed in a significant minority ofpatients following a selective neck dissection. SublevelIA is another example in which many surgeons optnot to remove this zone unless the primary cancer in-volves the floor of mouth, lip, or structures of the ante-rior midface.

Level V is the third region in which the committeebelieved there was merit in subdividing it into levels VAand VB. The superior component, level VA, primarilycontains the spinal accessory lymph nodes, whereaslevel VB contains the transverse cervical nodes and thesupraclavicular nodes, which carry a far more ominousprognosis when positive for aerodigestive tract malig-nancies.

III

IIIVI

V

IV

Figure 1. The 6 levels of the neck.

IA

IB

IIA

IIB

III

VI

VA

VBIV

Figure 2. The 6 sublevels of the neck.

Table 1. Classification of Neck Dissection

1991 Classification1 2001 Classification

1. Radical neck dissection 1. Radical neck dissection2. Modified radical neck

dissection2. Modified radical neck

dissection3. Selective neck dissection

(a) Supraomohyoid(b) Lateral(c) Posterolateral(d) Anterior

3. Selective neck dissection:each variation is depicted by“SND” and the use ofparentheses to denote thelevels or sublevels removed

4. Extended neck dissection 4. Extended neck dissection



DEFINITION OF LYMPH NODE GROUPS

It was agreed that the names depicting the lymph nodegroups within each of the 6 neck levels were well ac-cepted and used in a uniform manner (Table 2). Con-tinued support of this nomenclature would preclude theintroduction of other terms that would potentially be am-biguous (eg, deep cervical nodes). Table 2 also outlinesthe lymph node groups located within each of the 6 necklevels.

ANATOMICAL BOUNDARIESOF THE NECK LEVELS

The anatomical boundaries of the 6 neck levels as identi-fied in the first article on neck dissection classification werewell defined with the exception of a few instances in whichthere were minor inaccuracies or ambiguities (Table 3).1

For example, the stylohyoid muscle rather than the pos-terior belly of the digastric muscle more accurately de-fines the posterior border of level IB. Similarly, the planedefined by the sensory branches of the cervical plexus hasbeen added to delineate the boundary between the poste-

rior borders of levels II through IV and the anterior bor-der of level V. This parameter is in addition to the poste-rior border of the sternocleidomastoid muscle (SCM)and provides a more practical intraoperative landmarkfor the surgeon (Table 3 and Figure 2).

CORRELATION OF NECK LEVEL BOUNDARIESWITH ANATOMICAL MARKERSDEPICTED RADIOLOGICALLY

In the 1991 neck dissection classification,1 not all of theanatomical structures used to define the boundaries werereadily visible on radiologic studies such as computedtomography and magnetic resonance imaging. Conse-quently, radiologists have now identified landmarks thatmore accurately identify the location of lymph nodes ac-cording to the level system.3 Using radiologic land-marks, level I includes all of the nodes above the level ofthe lower body of the hyoid bone, below the mylohyoidmuscles, and anterior to a transverse line drawn on eachaxial image through the posterior edge of the subman-dibular gland. Level IA represents those nodes that liebetween the medial margins of the anterior bellies of the

Table 2. Lymph Node Groups Found Within the 6 Levels and the 6 Sublevels

Lymph Node Group Description

Submental (sublevel IA) Lymph nodes within the triangular boundary of the anterior belly of the digastric muscles and the hyoid bone. These nodes are atgreatest risk for harboring metastases from cancers arising from the floor of mouth, anterior oral tongue, anterior mandibularalveolar ridge, and lower lip (Figure 2).

Submandibular(sublevel IB)

Lymph nodes within the boundaries of the anterior belly of the digastric muscle, the stylohyoid muscle, and the body of themandible. It includes the preglandular and the postglandular nodes and the prevascular and postvascular nodes. Thesubmandibular gland is included in the specimen when the lymph nodes within the triangle are removed. These nodes are atgreatest risk for harboring metastases from cancers arising from the oral cavity, anterior nasal cavity, soft tissue structures ofthe midface, and submandibular gland (Figure 3).

Upper jugular (includessublevels IIA and IIB)

Lymph nodes located around the upper third of the internal jugular vein and adjacent spinal accessory nerve extending from thelevel of the skull base (above) to the level of the inferior border of the hyoid bone (below). The anterior (medial) boundary is thestylohyoid muscle (the radiologic correlate is the vertical plane defined by the posterior surface of the submandibular gland) andthe posterior (lateral) boundary is the posterior border of the sternocleidomastoid muscle. Sublevel IIA nodes are locatedanterior (medial) to the vertical plane defined by the spinal accessory nerve. Sublevel IIB nodes are located posterior (lateral) tothe vertical plane defined by the spinal accessory nerve. The upper jugular nodes are at greatest risk for harboring metastasesfrom cancers arising from the oral cavity, nasal cavity, nasopharynx, oropharynx, hypopharynx, larynx, and parotid gland (Figure3).

Middle jugular (level III) Lymph nodes located around the middle third of the internal jugular vein extending from the inferior border of the hyoid bone(above) to the inferior border of the cricoid cartilage (below). The anterior (medial) boundary is the lateral border of thesternohyoid muscle, and the posterior (lateral) boundary is the posterior border of the sternocleidomastoid muscle. Thesenodes are at greatest risk for harboring metastases from cancers arising from the oral cavity, nasopharynx, oropharynx,hypopharynx, and larynx (Figure 3).

Lower jugular (level IV) Lymph nodes located around the lower third of the internal jugular vein extending form the inferior border of the cricoid cartilage(above) to the clavicle below. The anterior (medial) boundary is the lateral border of the sternohyoid muscle and the posterior(lateral) boundary is the posterior border of the sternocleidomastoid muscle. These nodes are at greatest risk for harboringmetastases from cancers arising from the hypopharynx, thyroid, cervical esophagus, and larynx (Figure 3).

Posterior triangle group(includes sublevels VAand VB)

This group is composed predominantly of the lymph nodes located along the lower half of the spinal accessory nerve and thetransverse cervical artery. The supraclavicular nodes are also included in posterior triangle group. The superior boundary isthe apex formed by convergence of the sternocleidomastoid and trapezius muscles, the inferior boundary is the clavicle, theanterior (medial) boundary is the posterior border of the sternocleidomastoid muscle, and the posterior (lateral) boundary is theanterior border of the trapezius muscle. Sublevel VA is separated from sublevel VB by a horizontal plane marking the inferiorborder of the anterior cricoid arch. Thus, sublevel VA includes the spinal accessory nodes, whereas sublevel VB includes thenodes following the transverse cervical vessels and the supraclavicular nodes with the exception of the Virchow node, which islocated in level IV. The posterior triangle nodes are at greatest risk for harboring metastases from cancers arising from thenasopharynx, oropharynx, and cutaneous structures of the posterior scalp and neck (Figure 3).

Anterior compartmentgroup (level VI)

Lymph nodes in this compartment include the pretracheal and paratracheal nodes, precricoid (Delphian) node, and theperithyroidal nodes including the lymph nodes along the recurrent laryngeal nerves. The superior boundary is the hyoid bone,the inferior boundary is the suprasternal notch, and the lateral boundaries are the common carotid arteries. These nodes are atgreatest risk for harboring metastases from cancers arising from the thyroid gland, glottic and subglottic larynx, apex of thepiriform sinus, and cervical esophagus (Figure 2).



digastric muscles, above the level of the lower body ofthe hyoid bone, and below the mylohyoid muscle (pre-viously classified as submental nodes). Level IB repre-sents the nodes that lie below the mylohyoid muscle,above the level of the lower body of the hyoid bone, pos-terior and lateral to the medial edge of the anterior bellyof the digastric muscle, and anterior to a transverse linedrawn on each axial image tangent to the posterior sur-face of the submandibular gland on each side of the neck(previously classified as submandibular nodes). Level IIextends from the skull base, at the lower level of the bonymargin of the jugular fossa, to the level of the lower bodyof the hyoid bone. Level II nodes lie anterior to a trans-verse line drawn on each axial image through the pos-terior edge of the SCM and lie posterior to a transverseline drawn on each axial scan through the posterior edgeof the submandibular gland. However, any nodes that liemedial to the internal carotid artery are retropharyngealand not level II.

Level III nodes lie between the level of the lowerbody of the hyoid bone and the level of the lower mar-gin of the cricoid cartilage. These nodes lie anterior to atransverse line drawn on each axial image through theposterior edge of the SCM. Level III nodes also lie lateralto the medial margin of either the common carotidartery or the internal carotid artery. On each side of theneck, the medial margin of these arteries separates levelIII nodes (which are lateral) from level VI nodes (whichare medial).

Thus, the revised classification uses the horizontalplane defined by the inferior border of the hyoid boneinstead of the carotid bifurcation to delineate the bound-ary between levels II and III. Similarly, the revised clas-sification uses the horizontal plane defined by the infe-rior border of the cricoid cartilage instead of the junctionbetween the superior belly of the omohyoid muscle to

delineate the boundary between level III and level IV.However, from a surgical perspective it is important tonote the significance of the anatomical relationship be-tween the omohyoid muscle and the internal jugular vein,since lymph nodes usually are located in this region. Thesenodes would be included in level III.

CONCEPTUAL GUIDELINESFOR NECK DISSECTION CLASSIFICATION

The definitions of types of neck dissection remain un-changed as previously outlined in the 1991 classifica-tion article.1 These are (1) radical neck dissection is con-sidered to be the standard basic procedure for cervicallymphadenectomy, and all other procedures represent 1or more alterations of this procedure; (2) when the al-teration involves preservation of 1 or more nonlymphaticstructures routinely removed in the radical neck dissec-tion, the procedure is termed modified radical neck dis-section; (3) when the alteration involves preservation of1 or more lymph node groups/levels routinely removed inthe radical neck dissection, the procedure is termed se-lective neck dissection; (4) when the alteration involvesremoval of additional lymph node groups or nonlymphaticstructures relative to the radical neck dissection, the pro-cedure is termed extended neck dissection.

CLASSIFICATION OF NECK DISSECTION

Classification of neck dissection is outlined in Table 1. Itis essentially the same as the 1991 version1 with the ex-ception that specific names for certain types of selectiveneck dissection have been deleted. As outlined in the sec-tion on selective neck dissection, the rationale for this rec-ommendation is based on the increased number of varia-tions, which have been introduced over the past decade.

Table 3. Anatomical Structures Defining the Boundaries of the Neck Levels and Sublevels

Level

Boundary

Superior Inferior Anterior (Medial) Posterior (Lateral)

IA Symphysis of mandible Body of hyoid Anterior belly of contralateraldigastric muscle

Anterior belly of ipsilateral digastricmuscle

IB Body of mandible Posterior belly of muscle Anterior belly of digastric muscle Stylohyoid muscleIIA Skull base Horizontal plane defined by the inferior

body of the hyoid boneStylohyoid muscle Vertical plane defined by the spinal

accessory nerveIIB Skull base Horizontal plane defined by the inferior

body of the hyoid boneVertical plane defined by the

spinal accessory nerveLateral border of the

sternocleidomastoid muscleIII Horizontal plane defined by

inferior body of hyoidHorizontal plane defined by the inferior

border of the cricoid cartilageLateral border of the sternohyoid

muscleLateral border of the

sternocleidomastoid or sensorybranches of cervical plexus

IV Horizontal plane defined bythe inferior border of thecricoid cartilage

Clavicle Lateral border of the sternohyoidmuscle

Lateral border of thesternocleidomastoid or sensorybranches of cervical plexus

VA Apex of the convergence ofthe sternocleidomastoidand trapezius muscles

Horizontal plane defined by the lowerborder of the cricoid cartilage

Posterior border of thesternocleidomastoid muscle orsensory branches of cervicalplexus

Anterior border of the trapeziusmuscle

VB Horizontal plane defined bythe lower border of thecricoid cartilage

Clavicle Posterior border of thesternocleidomastoid muscle orsensory branches of cervicalplexus

Anterior border of the trapeziusmuscle

VI Hyoid bone Suprasternal Common carotid artery Common carotid artery



RADICAL NECK DISSECTION

Radical neck dissection (Figure 3) refers to the re-moval of all ipsilateral cervical lymph node groups ex-tending from the inferior border of the mandible to theclavicle, from the lateral border of the sternohyoid muscle,hyoid bone, and contralateral anterior belly of the digas-tric muscle medially, to the anterior border of the trape-zius muscle. Included are all lymph nodes from levels Ithrough V. The SAN, internal jugular vein, and SCM arealso removed. Radical neck dissection does not includeremoval of the suboccipital nodes, periparotid nodes (ex-cept intraparotid nodes located in the posterior aspect

of the submandibular triangle), buccinator nodes, ret-ropharyngeal nodes, and midline visceral (anterior com-partment) nodes.

MODIFIED RADICAL NECK DISSECTION

Modified radical neck dissection (Figures 4, 5, and 6)refers to the excision of all lymph nodes routinely re-moved by the radical neck dissection with preservationof 1 or more nonlymphatic structures (ie, the SAN, in-ternal jugular vein, and SCM). The structure(s) pre-served should be specifically named (eg, modified radi-cal neck dissection with preservation of the SAN).

Figure 3. The radical neck dissection.

Figure 4. Modified radical neck dissection with preservation of thesternocleidomastoid muscle, spinal accessory nerve, and internal jugularvein.

Figure 5. Modified radical neck dissection with preservation of the internaljugular vein and spinal accessory nerve.

Figure 6. Modified radical neck dissection with preservation of spinalaccessory nerve.



SELECTIVE NECK DISSECTION

Selective neck dissection refers to a cervical lymphadenec-tomy in which there is preservation of 1 or more of thelymph node groups that are routinely removed in the radi-cal neck dissection. The lymph node groups removed arebased on the patterns of metastases, which are predictablerelative to the primary site of disease. For oral cavity can-cers, the lymph nodes at greatest risk are located in levelsI, II, and III. The lymph nodes at greatest risk for oropha-ryngeal, hypopharyngeal, and laryngeal cancers are lo-cated in levels II, III, and IV, whereas for thyroid cancer,the lymph nodes in VI are at the greatest risk.

Refinements inSelective Neck Dissection Nomenclature

Probably the most significant change in philosophy withregard to managing lymph node disease over the past de-caderelates totheselectivitywithwhichlymphnodegroupsat riskarebeingremoved.6 Withoutquestion, theuseof theselective neck dissection has become more widespread de-spite some earlier concerns that it may not be as effectiveas neck dissections in which all lymph node levels are re-moved, such as the modified radical neck dissection. How-ever, of equal significance have been the reports indicatingthatcertainneck levelsmayhave lessorgreater importancethan previously thought with regard to risk of occult dis-ease based on the specific site of origin of the primary tu-mor. An excellent example of this is carcinoma of the oraltongue. Although it is well appreciated that patients withoral tongue cancer have a high risk of nodal involvementeven for those with small primary lesions without clinicalevidence of positive nodes, the extent by which the risk re-mains high for each neck level is controversial. Skip me-tastases to level IV may be a potential problem, and manysurgeons prefer to include this region when performing anelective selective neck dissection. However, the terminol-

ogy to describe the neck dissection procedure for this situ-ation is vague. Some prefer to apply the term supraomo-hyoid neck dissection because this is the standard electiveprocedure typically used for oral tongue cancer. But this isinaccuratebecausesupraomohyoidneckdissectionwas in-tended to include only levels I through III. Others preferto use the term extended supraomohyoid neck dissection oranterolateralneckdissection,whichmoreaccuratelyoutlinesthe removal of levels I through IV. Unfortunately, accep-tance of these additional terms adds complexity to the no-menclature system and runs the risk of adding confusion.

The 1991 neck dissection classification system didnot provide an accurate description of procedures in whichthe surgeon chooses to preserve certain sublevels. Forexample, the buccinator nodes may represent the pri-mary echelon nodal basin for oral cavity cancers involv-ing the buccal mucosal, hard palate, and upper alveolarridge. These nodes are not included in the standard su-praomohyoid neck dissection, and a better method isneeded to define the inclusion of such structures. To notfurther confuse this issue, it was determined by the com-mittee that exclusion of these “named” neck dissectionswould facilitate the standardization and referencing ofthese procedures. Therefore, further in this text, we willno longer refer to these “named” selective neck dissec-tions except in the description of specific levels.

Selective Neck Dissection (SND)for Oral Cavity Cancer

In the treatment of oral cavity cancer, the procedure ofchoice is SND (I-III) (Figure 7). This refers to the re-moval of lymph nodes contained in the submental and sub-mandibular triangles (level I), the upper jugular lymphnodes (level II), and the middle jugular lymph nodes (levelIII). The cutaneous branches of the cervical plexus andthe posterior border of the SCM mark the posterior limitof the dissection. The inferior limit is the junction be-tween the superior belly of the omohyoid muscle and theinternal jugular vein. One of the justifications to elimi-nate naming of dissections for oral cavity cancer comes fromthe observations regarding invasive oral tongue carcino-mas. In the case of oral tongue cancer, there is evidenceindicating level IV is also at risk.7 Thus, some authoritiesrecommend the selective neck dissection procedure for thissubsite within the oral cavity to be SND (I-IV). For can-cers involving the midline structures including the floorof mouth and ventral tongue, the lymph nodes on both sidesof the neck are at risk and the procedure of choice is abilateral SND (I-III).

Selective Neck Dissection for Oropharyngeal,Hypopharyngeal, and Laryngeal Cancer

The procedure of choice for these anatomic sites is SND(II-IV) (Figure 8). This refers to the removal of the up-per jugular lymph nodes (level II), the middle jugularlymph nodes (level III), and the lower jugular lymphnodes (level IV). The superior limit of dissection is theskull base. The inferior limit is the clavicle. The anterior(medial) limit is the lateral border of the sternohyoidmuscle and the stylohyoid muscle. The posterior (lat-

IB

IA

IIB

IIA

III

Figure 7. Selective neck dissection (SND) for oral cavity cancer: SND (I-III)or supraomohyoid neck dissection.



eral) limit of the dissection is marked by the cutaneousbranches of the cervical plexus and the posterior borderof the SCM. In the case of cancers involving the orophar-ynx, there is evidence indicating that the lateral and ret-ropharyngeal nodes are also at risk. Similarly, cancers ofthe hypopharynx may involve the retropharyngeal lym-phatics. Level IIB is at greater risk for metastases asso-ciated with oropharyngeal lesions relative to laryngeal andhypopharyngeal cancers. Thus, if level IIB is excludedas is sometimes done for laryngeal and hypopharyngealcancers, the procedure would be designated SND (IIA,III, IV). When lymphatic metastases occur bilaterally, theprocedure of choice is a bilateral SND (II-IV). If the ret-ropharyngeal lymph nodes are included, as in the caseof cancers involving the pharyngeal wall, the procedureis designated SND (II-IV), retropharyngeal nodes. If thenodes in level VI are removed, as in the case of laryngealand hypopharyngeal cancers extending below the levelof the glottis, the procedure is designated SND (II-IV, VI).

Selective Neck Dissection for Cancer ofthe Midline Structures of the Anterior Lower Neck

For cancer of the midline structures of the anterior lowerneck, the procedure of choice is SND (VI) and is most of-ten indicated with or without dissection of other neck lev-els for thyroid cancer, advanced glottic and subglottic lar-ynx cancer, advanced piriform sinus cancer, and cervicalesophageal/tracheal cancer (Figure 9). This SND refersto the removal of the lymph nodes within the central com-partment of the neck including the paratracheal, precri-coid (Delphian), and perithyroidal lymph nodes as well asthe nodes located along the recurrent laryngeal nerves. Thesuperior limit of dissection is the body of the hyoid bone,and the inferior limit is the suprasternal notch. The laterallimits are defined by the medial border of the carotid sheath(common carotid artery). This procedure is also known asthe anterior neck dissection or the central compartmentneck dissection. This neck dissection does not have a con-tralateral counterpart, and it assumes that the lymph nodesare removed on both sides of the trachea. In the case of me-tastases extending below the level of the suprasternal notch,dissection of the superior mediastinal nodes may be indi-cated, in which case the procedure is designated SND (VI,superior mediastinal nodes). In the case of thyroid cancerin which there is evidence of nodal metastases into levelV, the procedure of choice would include the jugular nodesas well as the posterior triangle nodes and would be des-ignated SND (II-V, VI).

Selective Neck Dissectionfor Cutaneous Malignancies

For cutaneous malignancies, the operation of choice de-pends on the location of the lesion and the adjacent lymphnode groups, which are most likely to harbor metastaticdisease (Figure 10). In the case of cancers involving theposterior scalp and upper neck, the procedure of choice isSND (II-V, postauricular, suboccipital) (Figure 9). It in-volves the removal of the suboccipital lymph nodes, ret-roauricular lymph nodes, upper jugular lymph nodes (levelII), middle jugular lymph nodes (level III), lower jugular

(level IV), and the nodes of the posterior triangle of the neck(level V). The superior limit of dissection is the skull baseanteriorly and the nuchal ridge posteriorly. The inferior limitis the clavicle. The medial (anterior) limit is the lateral bor-der of the sternohyoid muscle and the stylohyoid muscle.The lateral (posterior) limit is the anterior border of thetrapezius muscle inferiorly and the midline of the neck su-periorly. For cutaneous malignancies arising on the pre-auricular, anterior scalp, and temporal region, the electiveneck dissection of choice is SND (parotid and facial nodes,levels IIA, IIB, III, VA, and the external jugular nodes). Forcutaneous malignancies arising on the anterior and lateralface, the elective neck dissection of choice is SND (pa-rotid and facial nodes, levels IA, IB, II, and III). The devel-opment of techniques in lymphatic mapping may have afuture role in specifically defining nonpredictable lym-phatic echelons of risk for cutaneous malignancies.

IIB

IIA

III

IV

Figure 8. Selective neck dissection (SND) for oropharyngeal,hypopharyngeal, and laryngeal cancer: SND (II-IV) or lateral neck dissection.

VI

Figure 9. Selective neck dissection (SND) for thyroid cancer: SND (VI) oranterior neck dissection.



EXTENDED NECK DISSECTION

Extended neck dissection refers to the removal of 1 ormore additional lymph node groups or nonlymphaticstructures, or both, not encompassed by the radical neckdissection (Figure 11). Examples of such lymph nodegroups include the parapharyngeal (retropharyngeal), su-perior mediastinal, perifacial (buccinator), and paratra-cheal lymph nodes. Examples of nonlymphatic struc-tures include the carotid artery, hypoglossal nerve, vagusnerve, and paraspinal muscles. All additional lymphaticand/or nonlymphatic structure(s) to be removed shouldbe identified in parentheses.

SUMMARY

The material outlined in the present article is not sub-stantially different from the recommendations1 made by

the Academy’s Committee on Neck Dissection a decadeago. The need to make such few changes reflects the suc-cess of the initial efforts made by this committee and theacceptance by head and neck surgeons of the Academy’sclassification. Nonetheless, the knowledge of lymph nodemetastases based on biological and clinical perspectivescontinues to evolve. The changes made in this update areintended to represent further refinements of our under-standing of the biological basis of cervical node metas-tases and how neck dissection is performed under vari-ous circumstances. Consensus on which anatomicalstructures best define the locations of lymph node groupsand the boundaries of dissection is also important for com-municating among clinicians. The committee also be-lieves that this article represents a work in progress, andthere will be a need to provide future updates as newknowledge and techniques evolve. This article repre-sents a consensus among representative head and necksurgeons of the ASHNS and the AAO-HNS to further de-fine the essential definitions and concepts outlined in thisupdated classification.

Accepted for publication April 5, 2002.This study was presented at the Fifth International

Conference on Head and Neck Cancer, San Francisco, Calif,July 30, 2000.

The authors wish to acknowledge the efforts of Doug-las Denys for his excellent artwork.

Corresponding author and reprints: K. Thomas Rob-bins, MD, Department of Otolaryngology, University ofFlorida, PO Box 100264, Gainesville, FL 32610-0264(e-mail: [email protected]).

REFERENCES

1. RobbinsKT,MedinaJE,WolfeGT,LevineP,SessionsR,PruetC.Standardizingneckdissection terminology. Arch Otolaryngol Head Neck Surg. 1991;117:601-605.

2. Robbins KT, ed. Pocket Guide to Neck Dissection, Classification and TNM Stag-ing of Head and Neck Cancer. Alexandria, Va: American Academy of Otolaryn-gology Head and Neck Surgery Foundation; 2001.

3. Som PM, Curtin HD, Mancuso AA. An imaging-based classification for the cer-vical nodes designed as an adjunct to recent clinically based nodal classifica-tions. Arch Otolaryngol Head Neck Surg. 1999;125:388-396.

4. Robbins KT. Integrating radiologic criteria into the classification of cervical lymphnode disease. Arch Otolaryngol Head Neck Surg. 1999;125:385-387.

5. Shah J, Strong E, Spiro R, Vikram B. Surgical grand rounds: neck dissection—current status and future possibilities. Clin Bull. 1981;11:25-33.

6. Robbins KT. Indications for selective neck dissection: when, how, and why. On-cology. 2000;14:1455-1469.

7. Byers RM, Weber RS, Andrews T, McGill D, Kare R, Wolf P. Frequency and thera-peutic implications of “skip metastases” in the neck from squamous carcinomaof the oral tongue. Head Neck. 1997;19:14-19.

IIA

IIB

IIIVA

VBIV

Figure 10. Selective neck dissection (SND) for posterior scalp and upperposterolateral neck cutaneous malignancies: SND (II-V), postauricular,suboccipital) or posterolateral neck dissection.

Figure 11. Extended neck dissection (common carotid artery).

Study Group

The Committee for Head and Neck Surgeryand Oncology, AAO-HNS

G. Clayman, MD (chair); T. Day, MD; W. Koch, MD;J. H. Boyd, MD; F. Miller, MD; J. Cohen, MD; J. Myers,MD; S. Eicher, MD; C. Snyderman, MD; R. Esclamado,MD; S. Stern, MD; N. Futran, MD; R. Weber, MD;L. Gleich, MD; J. Suen, MD; G. Har-El, MD; B. Camp-bell, MD; G. Hartig, MD; and W. J. Goodwin, MD



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