2 Introduction to Head and Neck Sites
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SUMMARY OF CHANGES
• Across the board for all head and neck sites, a uniform description of advanced tumors has been recommended whereby T4 lesions are divided into T4a (resectable) and T4b (unresectable). This will allow assignment of patients with advanced stage disease to three categories: Stage IVA, advanced resectable disease;
Stage IVB, advanced unresectable disease; and Stage IVC, advanced distant metastatic disease.
• In general, every effort has been made to bring the stage groupings to a relatively uniform combination of T, N, and M categories for all sites, including paranasal sinuses, salivary tumors, and thyroid tumors.
• No changes have been made in the N staging for any sites except that a descrip- tor has been added for nodal metastasis in the upper neck or in the lower neck, designated by (U) and (L) respectively. This descriptor will not influence nodal staging.
INTRODUCTION
Cancers of the head and neck may arise from any of the lining membranes of the upper aerodigestive tract. The T classifications indicating the extent of the primary tumor are generally similar but differ in specific details for each site because of anatomic considerations. The N classification for cervical lymph node metastasis is uniform for all mucosal sites except nasopharynx. The N clas- sifications for thyroid and nasopharynx are unique to those sites and are based on tumor behavior and prognosis. The staging systems presented in this section are all clinical staging based on the best estimate of the extent of disease before first treatment. Imaging techniques (computed tomography [CT], magnetic res- onance imaging [MRI], and ultrasonography) may be applied and, in more advanced tumor stages, have added to the accuracy of primary (T) and nodal (N) staging, especially in the nasopharyngeal, paranasal sinuses, and regional lymph nodal areas. Appropriate imaging studies should be obtained whenever the clinical findings are uncertain. Similarly, endoscopic evaluation of the primary tumor, when appropriate, is desirable for detailed assessment of the primary tumor for accurate T staging. Fine-needle aspiration (FNAB) may confirm the presence of tumor and its histopathologic nature, but it cannot rule out the presence of tumor.
Any diagnostic information that contributes to the overall accuracy of the pretreatment assessment should be considered in clinical staging and treatment planning. When surgical treatment is carried out, cancer of the head and neck can be staged (pathologic stage [pTNM]) using all information available from clinical assessment, as well as from the pathologic study of the resected speci- men. The pathologic stage does not replace the clinical stage, which should be reported as well.
In reviewing the staging systems, several changes in the T classifications as well as the stage groupings are made to reflect current practices of treatment,
clinical relevance, or contemporary data. Uniform T staging for oral cavity, oropharynx, salivary, and thyroid cancers greatly simplifies the systems and will improve compliance by clinicians. T4 tumors are subdivided into advanced resectable (T4a) and advanced unresectable (T4b) categories. Regrouping of Stage IV disease for all sites into advanced resectable (Stage IVA), advanced unresectable (Stage IVB), and distant metastatic (Stage IVC) also simplifies advanced-disease staging.
Chapters 3 through 8 present the illustrated staging classification for six major head and neck regions: the oral cavity, the pharynx (nasopharynx, oropharynx, and hypopharynx), the larynx, the paranasal sinuses, the salivary glands, and the thyroid gland.
ANATOMY
Regional Lymph Nodes. The status of the regional lymph nodes in head and neck cancer is of such prognostic importance that the cervical nodes must be assessed for each patient and tumor. The lymph nodes may be subdivided into specific anatomic subsites and grouped into seven levels for ease of description.
Level I: Submental Submandibular Level II: Upper jugular Level III: Mid-jugular Level IV: Lower jugular
Level V: Posterior triangle (spinal accessory and transverse cervical) (upper, middle, and lower, corresponding to the levels that define upper, middle, and lower jugular nodes)
Level VI: Prelaryngeal (Delphian) Pretracheal
Paratracheal Level VII: Upper mediastinal Other groups: Sub-occipital
Retropharyngeal Parapharyngeal Buccinator (facial) Preauricular
Periparotid and intraparotid
The location of the lymph node levels conforms to the following clinical descriptions, which also correlate with surgical landmarks at the time of surgi- cal neck exploration (Figures 2.1, 2.2, 2.3).
Level I: Contains lymph nodes in the submental and submandibular trian- gles bounded by the anterior and posterior bellies of the digastric muscle, and the hyoid bone inferiorly, and the body of the mandible superiorly.
Level II: Contains lymph nodes in the upper jugular lymph nodes and extends from the level of the skull base superiorly to the hyoid bone inferiorly.
Level III: Contains the middle jugular lymph nodes from the hyoid bone superiorly to the level of the lower border of the cricoid cartilage inferiorly.
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I I
VI
II II
IV III
V
FIGURE 2.1. Schematic diagram indicating the location of the lymph node levels in the neck as described in the text.
Buccal
Preauricular and intraparotid
Retroauricular and sub-occipital
FIGURE 2.2. Location of parotid, buccal, retroauricular and occipital nodes.
Retropharyngeal
FIGURE 2.3. Location of retropharyngeal nodes.
Level IV: Contains the lower jugular lymph nodes from the level of the cricoid cartilage superiorly to the clavicle inferiorly.
Level V: Contains the lymph nodes in the posterior triangle bounded by the anterior border of the trapezius muscle posteriorly, the poste- rior border of the sternocleidomastoid muscle anteriorly, and the clavicle inferiorly. For descriptive purposes, Level V may be further subdivided into upper, middle, and lower levels correspon- ding to the superior and inferior planes that define Levels II, III, and IV.
Level VI: Contains the lymph nodes of the anterior central compartment from the hyoid bone superiorly to the suprasternal notch inferiorly.
On each side, the lateral boundary is formed by the medial border of the carotid sheath.
Level VII: Contains the lymph nodes inferior to the suprasternal notch in the superior mediastinum.
The pattern of the lymphatic drainage varies for different anatomic sites.
However, the location of the lymph node metastases has prognostic significance in patients with squamous cell carcinoma of the head and neck. Survival is sig- nificantly worse when metastases involve lymph nodes beyond the first echelon of lymphatic drainage and, particularly, lymph nodes in the lower region of the neck, i.e., Level IV and Level V (supraclavicular region). Consequently, it is rec- ommended that each N staging category be recorded to show, in addition to the established parameters, whether the nodes involved are located in the upper (U) or lower (L) regions of the neck, depending on their location above or below the lower border of the cricoid cartilage.
The natural history and response to treatment of cervical nodal metastases from nasopharynx primary sites are different, in terms of their impact on prog- nosis, so they justify a different N classification scheme. Regional nodal metas- tases from well-differentiated thyroid cancer do not significantly affect the ultimate prognosis and therefore also justify a unique staging system for thyroid cancers.
Histopathologic examination is necessary to exclude the presence of tumor in lymph nodes. No imaging study (as yet) can identify microscopic tumor foci in regional nodes or distinguish between small reactive nodes and small malig- nant nodes.
When enlarged lymph nodes are detected, the actual size of the nodal mass(es) should be measured. It is recognized that most masses over 3 cm in diameter are not single nodes but are confluent nodes or tumor in soft tissues of the neck. Imaging studies showing amorphous spiculated margins of involved nodes or involvement of intranodal fat resulting in loss of normal oval to round nodal shape strongly suggest extracapsular (extranodal) tumor spread. Patho- logic examination is necessary for documentation of tumor extent in terms of the location or level of the lymph node(s) involved, the number of nodes that contain metastases, and the presence or absence of extracapsular spread of tumor.
Metastatic Sites. The most common sites of distant spread are in the lungs and bones; hepatic and brain metastases occur less often. Mediastinal lymph node metastases are considered distant metastases.
Regional Lymph Nodes (N) (Figure 2.4) NX Regional lymph nodes cannot be assessed N0 No regional lymph node metastasis
*N1 Metastasis in a single ipsilateral lymph node, 3 cm or less in greatest dimension
*N2 Metastasis in a single ipsilateral lymph node, more than 3 cm but not more than 6 cm in greatest dimension; or in multiple ipsilateral lymph nodes, none more than 6 cm in greatest dimension; or in bilateral or contralateral lymph nodes, none more than 6 cm in greatest dimension
*N2a Metastasis in single ipsilateral lymph node more than 3 cm but not more than 6 cm in greatest dimension
*N2b Metastasis in multiple ipsilateral lymph nodes, none more than 6 cm in greatest dimension
*N2c Metastasis in bilateral or contralateral lymph nodes, none more than 6 cm in greatest dimension
*N3 Metastasis in a lymph node more than 6 cm in greatest dimension
*Note: A designation of “U” or “L” may be used to indicate metastasis in the lateral neck above the lower border of the cricoid (U) or below the lower border of the cricoid (L).
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N0 N1 N2a
N2b N2c N3
Ipsilateral <3 cm Ipsilateral 3-6 cm
Bilateral or contralateral <6 cm
Ipsilateral multiple <6 cm >6 cm
FIGURE 2.4. Regional lymph node (N) classification for all head and neck cancer sites except nasopharynx and thyroid cancers.
Distant Metastasis (M)
MX Distant metastasis cannot be assessed M0 No distant metastasis
M1 Distant metastasis
