Management of the N0 Neck 

Updated: Feb 19, 2020
Author: Mohamad R Chaaban, MD, MBA, MSCR, FACS, FAAOA; Chief Editor: Arlen D Meyers, MD, MBA 

Overview

Background

The treatment of patients with N0 squamous cell carcinoma (SCCA) of the head and neck remains controversial. The negative impact of regional lymph node metastases on the survival in patients with SCCA of the upper aerodigestive tract has been well established. The presence of lymph node metastases is the most important prognostic factor for survival in head and neck SCCA. Histologically proven lymph node metastasis increases the stage to 3 and may decrease survival by 50%.

Watchful waiting until a patient with an N0 neck develops detectable neck disease has been shown to significantly decrease survival. Elective or prophylactic neck dissection improves regional control, and the results of salvage surgery for N0 neck, which were observed and have progressed to N+ neck, are poor. Therefore, the challenge of caring for patients with an N0 neck lies in identifying which patients are at risk for developing lymph node metastases in order to treat those patients prophylactically and to decrease the risk of neck failure in the neck.

The levels of metastasis to cervical lymph nodes can be seen in the image below.

Levels of metastasis to cervical lymph nodes. Levels of metastasis to cervical lymph nodes.

Epidemiology

Frequency

The basic rule for prophylactic treatment of the N0 neck is to treat any patient whose risk of occult lymph node metastases is greater than 15-20%. The risk of regional lymph node metastases varies according to primary site and stage. Areas such as the glottis carry a relatively low risk (< 4% for a T1 lesion), whereas the risk in a site such as the tongue base is as high as 55%. The prevalence of occult neck metastases by site is as follows:

  • Floor of mouth - 25%

  • Oral tongue - 60%

  • Buccal mucosa - 20%

  • Retromolar trigone - 20%

  • Hard palate - 15%

  • Alveolus - 15%

  • Tonsil - 36%

  • Tongue base - 55%

  • Epiglottis - 15%

  • False vocal cord - 15%

  • Aryepiglottic fold - 30%

  • True vocal cord - 15%

  • Pyriform sinus - 65%

Pathophysiology

The following are the lymphatic drainage nodes and the corresponding tumor locations from which they receive drainage:

  • Level 1A nodes

    • Lip

    • Anterior mandibular alveolar ridge

    • Floor of the mouth

  • Level 1B nodes

    • Oral cavity

    • Anterior nasal cavity

    • Soft tissues and structure of the mid face

  • Level 2 nodes

    • Oral cavity

    • Nasal cavity

    • Nasopharynx

    • Oropharynx

    • Hypopharynx

    • Larynx

    • Parotid gland

  • Level 3 nodes

    • Oral cavity

    • Nasopharynx

    • Oropharynx

    • Hypopharynx

    • Larynx

  • Level 4 nodes

    • Hypopharynx

    • Larynx

    • Cervical esophagus

  • Level 5 nodes

    • Nasopharynx

    • Oropharynx

  • Level 6 nodes

    • Thyroid gland

    • Larynx (glottic and subglottic)

    • Apex of the pyriform sinus

    • Cervical esophagus

  • Retropharyngeal nodes

    • Nasopharynx

    • Maxilla

    • Tonsil

    • Oropharynx

    • Hypopharynx

    • Pyriform sinus

    • Parathyroid cancer

    • Cervical esophagus

Presentation

Obtain patient's history and perform a complete head and neck physical examination. Although detailing a proper history taking for a head and neck examination is beyond the scope of this chapter, the following signs and symptoms should increase the index of suspicion for possible malignancy:

  • Nerve deficit

  • Obstruction (nasal, airway, digestive)

  • Epistaxis

  • Persistent sore throat

  • Persistent globus sensation

  • Hoarseness

  • Stridor

  • Leukoplakia

  • Erythroplakia

  • Neck node

  • Masses or nodules in the head and neck region

  • Ulceration

  • Dysphagia

Indications

The indication for treating the N0 neck with surgery or radiation is a risk of occult metastases in excess of 15-20%.

Surgery (elective neck dissection) is indicated if the patient is undergoing surgery for the primary lesions. This approach allows accurate staging because it is supported by histologic studies.

A study by Pfisterer et al found that in patients with SCCA of the parotid gland who had an N0 neck, 5-year disease-specific survival was 78.3% for those who underwent elective neck dissection, compared with 51.1% for those who did not. The study used data from the Surveillance, Epidemiology, and End Results (SEER) registry.[1]

In a retrospective study, Philip and James recommended that level 1-3 ipsilateral neck dissection be performed in patients with intraoral maxillary SCCA with an N0 neck. The study, which included 39 patients, found that N0 patients who did not undergo neck dissection had a similar progression rate to disease development as patients with an N+ neck, while ipsilateral neck disease seemed to be resolved in N0 patients who underwent ipsilateral neck dissection.[2]

Radiation in N0 neck cases is indicated in the following situations:

  • Radiation of the primary site is possible.

  • The patient refuses surgery.

  • The patient has significant medical comorbidities such that surgery of this magnitude is contraindicated.

Relevant Anatomy

During physical examination or during neck dissection, anatomical boundaries are used to identify the lymph nodal levels. The radiologic boundaries are used as reference points during the reading of radiologic images and identification lymph node nodal levels.

The anatomical and radiologic nodal boundaries are as follows:

  • Level 1 (submental and submandibular lymph nodes)

    • Anatomic borders

      • Level 1A (submental nodes) boundaries include the anterior belly of digastric and hyoid bone.

      • Level 1B (submandibular nodes) boundaries include the anterior belly and posterior belly, body of the mandible, and the lymph nodes in the facial vessels.

    • Radiologic borders: Nodes are above the hyoid bone, superficial to the mylohyoid and anterior to the transverse line drawn through the posterior edge of the submandibular gland.

  • Level 2 (superior jugular nodes)

    • Anatomic borders

      • Lymph nodes are anterior to and behind the great vessels, extending from the skull base to the carotid bifurcation and between the sternohyoid muscle anteriorly and the posterior border of the sternocleidomastoid muscle posteriorly. Level 2 is further divided into A or B using CN 11 as an anatomical reference point.

      • Level 2A (nodes anterior to the spinal accessory nerves [CN 11])

      • Level 2B (nodes posterior to the spinal accessory nerve)

    • Radiologic borders: Lymph nodes are along the superior aspect of the jugular vein, extending from the skull base to the inferior aspect of the hyoid bone and between the back of the submandibular gland anteriorly and the posterior border of the sternocleidomastoid muscle posteriorly.

  • Level 3 (midjugular nodes)

    • Anatomic borders: Lymph nodes are along the middle third of the jugular vein. They are bounded superiorly by the carotid bifurcation, inferiorly by the omohyoid muscle, anteriorly by the sternohyoid muscle, and posteriorly by the border of the sternocleidomastoid muscle.

    • Radiologic borders: Lymph nodes are along the middle third of the jugular vein, extending from the bottom of the cricoid arch and between the sternohyoid muscle anteriorly and the posterior border of the sternocleidomastoid muscle posteriorly.

  • Level 4 (inferior jugular lymph nodes)

    • Anatomic borders: Lymph nodes are along the inferior aspect of the jugular vein and are bounded superiorly by the omohyoid muscle, inferiorly by the clavicle, anteriorly by the sternohyoid muscle, and posteriorly by the posterior border of the sternocleidomastoid muscle.

    • Radiologic borders: Lymph nodes are along the inferior aspect of the jugular vein, extending from the inferior aspect of the cricoid arch to the clavicle, and lying anterior to line connecting the posterior border of the sternocleidomastoid muscle and the posterolateral border of the anterior scalene muscle.

  • Level 5 (posterior triangle lymph nodes)

    • Anatomic borders

      • The posterior triangle lymph nodes are bounded anteriorly by the sternocleidomastoid muscle, posteriorly by the trapezius muscle, and inferiorly by the clavicle.

      • Level 5A: Nodes are superior to the level of the cricoid cartilage.

      • Level 5B: Nodes are inferior to the level of the cricoid cartilage.

    • Radiologic borders: Lymph nodes are bounded posteriorly by the trapezius muscle, inferiorly by the clavicle, anteriorly by the posterior border of the sternocleidomastoid muscle above the inferior border of the cricoid arch, and by the line connecting the posterior border of the sternocleidomastoid muscle and the posterolateral border of the anterior scalene muscle below the cricoid arch.

  • Level 6 (central compartment lymph nodes)

    • Anatomic borders: The lymph nodes are bounded superiorly by the hyoid bone, laterally by the carotid arteries, and inferiorly by the suprasternal notch.

    • Radiologic borders: Lymph nodes are bounded by the carotid sheath laterally, hyoid bone superiorly, and manubrium inferiorly.

  • Retropharyngeal nodes of Rouviere

    • Anatomic borders: The lymph nodes are posterior to the nasopharynx and oropharynx and medial to the carotid arteries.

    • Radiologic borders: Lymph nodes are from the skull base to T4 vertebrae.

 

Workup

Imaging Studies

Imaging of the cervical lymphatics alters the estimated clinical stage in 20-30% of patients.

Table 1. Evaluation of Neck Nodes (Open Table in a new window)

Modality

Sensitivity

Specificity

Ultrasound

50-58%

75-82%

CT

40-68%

78-92%

MRI

55-93%

82-95%

PET*

87-90%

80-93%

CT-PET

96%

98.5%

*Positron emission tomography.

Regardless of the type of imaging chosen, cervical lymph node must be considered to harbor metastasis if the any of the following criteria are met:

  • Node larger than 1 cm (or >1.5 cm in the jugulodigastric area)

  • Round node instead of oval

  • Internal central or peripheral attenuation suggestive of necrosis

  • Poorly defined mass in the lymph node–bearing area

  • The combination of ill-defined borders and loss of plane between mass and normal adjacent neck structures

  • Retropharyngeal node larger than 1 cm

  • Extracapsular extension

Chest radiography

Chest radiography is standard in the pretreatment evaluation of patients with head and neck cancer.

The incidence of pulmonary malignancy in head and neck cancer is 4.5-14%. The risk of secondary lung malignancy is high if the primary tumor originates from the larynx or pharynx.

The risk of a metachronous lesion in laryngeal cancer is 0.6% per year.

Patients with head and neck cancer have up to a 20% lifetime risk of developing secondary malignancy.

Ultrasonography of the neck

Ultrasonography is safe, fast, and inexpensive and can differentiate cystic from solid. In some institutions, it is used for evaluation of nodal metastasis. Ultrasound interpretation requires an experienced radiologist and is operator dependent.

CT scanning of the neck with contrast

Lymph nodes on a CT scan are considered suspicious only if they measure more than 1 cm (1.5 cm in the jugulodigastric area), are round instead of oval, or contain a necrotic center.

While this information may be helpful, normal CT scan findings do not rule out the possibility of metastatic disease and must be correlated with the incidence of occult metastasis and the stage of the disease.

Contrast is important in assessing neck disease. Without contrast, discerning pathologic adenopathy can be difficult.

Tumors usually enhance more than the surrounding muscle because of contrast. This facilitates identification of the pathologic condition.

MRI of the neck with gadolinium

MRI is superior to CT scanning in differentiating soft tissues. This is particularly helpful in assessing the extent of the primary tumor into surrounding soft tissues, especially in patients whose area of investigation on CT scan is affected by dental fillings.

In studying lymph node metastases, MRI is as accurate as CT scanning, and neither study has shown a clear-cut benefit over the other.

The choice of MRI versus CT scanning should be based on which will yield the most information about the primary lesion. For example, if bony invasion is suspected, CT scanning would be the study of choice because MRI resolution of bone in some instances may be inferior to that of CT. If extension of the tumor into the cranial cavity or perineural invasion is suspected, MRI is the study of choice because of its ability to differentiate between soft tissues structures and tumor.

PET scan

PET scan alone was considered unreliable in salivary gland tumors; however, in a recent study, Razfar et al demonstrated that CT-PET fusion can be very helpful in revealing unrecognized distant metastasis and/or local recurrence.[3, 4]

The PET detection rate in lymph nodes smaller than 1 cm is reported as 71%. A standard uptake value (SUV) of greater than 3 on a PET scan suggests malignancy.

CT-PET fusion

Studies suggest that fusion of CT scans and PET images has improved anatomical localization of abnormalities and tumors. It is useful in detecting recurrent cancer early, guiding biopsy, evaluating treatment results, and eliminating the need for additional imaging. Its role, however, in the initial staging of head and neck cancer with N0 neck remains to be proven. A 2010 study by Iyer et al concluded that CT-PET is not sufficiently accurate to guide therapeutic decisions in patients with an N0 neck.[5] In another study by Gilbert et al,[6] CT-PET fusion demonstrated a high false-negative rate, with 62.5% sensitivity and 70% negative predictive value in evaluating patients with recurrent laryngeal cancer. Because of this high false-negative rate, they recommended salvage neck dissection for patients with recurrence, along with salvage laryngectomy.

Histologic Findings

Histology is important in determining the best treatment for patients with oral cavity cancer and an N0 neck. Studies have been variable in the literature regarding the indication for elective neck dissection based on depth of invasion. In a study on T1/T2 oral SCCA, tumors with an invasion depth of more than 4 mm have been shown to have a significantly higher rate of occult lymph node metastasis and require prophylactic treatment of the neck. Although tumor thickness has been studied in other head and neck sites, including the larynx, this finding has proved to be significant only in the oral cavity cancer.[7]

A study by Lim et al regarding predictive markers for late cervical metastasis in stage 1 and 2 invasive SCCA of the oral tongue showed that, in a univariate analysis, tumor thickness, Broder grade, nest shape, mode of invasion, Anne Roth score, Byrne score, and E-cadherin expression correlated with late cervical metastasis.[8] Multivariate analysis in the same study also revealed that tumor thickness, mode of invasion, grade 3 or 4, and low E-cadherin expression were independent factors for cervical metastasis. Other variables for occult metastasis include age of over 65 years with advance T stage, vascular invasion, and perineural invasion.

 

Treatment

Medical Therapy

Treatment is planned after preoperative evaluation confirms the N0 status of the patient. If the likelihood of metastasis is low (< 15%), watchful waiting is appropriate. However, if the primary tumor contains aggressive characteristics such as perineural invasion, deep penetration (more than 3mm in the oral cavity), or angiolymphatic invasion, prophylactic treatment is necessary.[9]

Radiation has been shown to control regional recurrences in 95% of cases in which the primary site remains free of disease. Radiation has the advantage of decreased operative time, lacks the morbidity of neck dissection (shoulder discomfort), and is usually necessary to treat the primary site. Disadvantages include neck stiffness, skin changes, loss of hair in the treatment field, xerostomia, and increased morbidity and mortality if surgery in the irradiated area becomes necessary.[10]

Surgical Therapy

Surgery for the N0 neck has changed significantly and morbidity has greatly decreased. The first description of the radical neck dissection by George Crile in 1906 explains the importance of the fascial envelops that contains the lymph nodes that drain specific head and neck sites. These principles still apply today as the philosophy behind functional neck dissection.

Selective neck dissection is the mostly commonly used surgical therapy today in treating the N0 neck. The main advantages of selective neck dissection include pathologic identification of metastases (more accurate staging) and removal of occult disease. In selective neck dissection, nodal tissue is removed from the zones specifically related to the drainage patterns of a particular site. The internal jugular vein, sternocleidomastoid muscle (SCM), and spinal accessory nerve are preserved.

The oral cavity lymphatics drain into levels 1, 2, and 3, while the oropharynx, hypopharynx, and larynx drain into levels 2, 3, and 4.

Supraomohyoid neck dissection includes levels 1, 2, and 3 and is used to treat cancer of the oral cavity, some oropharyngeal cancers, and other cancers that drain to this nodal basin.

Lateral neck dissection includes levels 2, 3, and 4 and is used in patients with cancer of the hypopharynx, larynx, and other cancers that drain to this nodal basin. Level 2 dissection requires dissection of the fibrofatty tissue around the jugular, digastric, and spinal accessory nerve.

Modified radical neck dissection involves dissection of nodal basins 1-5 with preservation of the internal jugular vein, SCM, and the spinal accessory nerve. Because the incidence of nodal metastasis that involves level 5 in a clinically and radiologically negative neck or N0 neck is low (4%), the modified radical neck dissection is seldom used.

Retropharyngeal lymph node dissection is controversial for the N0 neck. The frequency of positive retropharyngeal node involvement in pyriform sinus with oropharyngeal invasion, postcricoid tumors, and tumors of the posterior wall are as follows:

  • Stage 1 - 3%

  • Stage 2 - 10.3%

  • Stage 3 - 9.8%

  • Stage 4 - 19.2%

In a study by Yoshimoto and Kawabata, patients with positive retropharyngeal nodes tend to have poor control rates; retropharyngeal node dissection did not improve survival.[11] A study on the prognostic influence of retropharyngeal adenopathy by Dirix noted more local recurrence (45%), and disease-free survival was significantly lower in the patients with retropharyngeal nodes. McLaughlin et al also noted that retropharyngeal adenopathy is a strong predictor of poor prognosis.[12] However, other studies by Shimizu et al and Gross et al revealed that no significant difference between survival rates and local recurrences can be found in patients with and without retropharyngeal lymph node metastasis.[13]

Another area of controversy is level 2B node dissection. A study by Elsheikh on level 2B nodes after supraomohyoid neck dissection for oral SCCA revealed that 31% were positive by histopathological analysis.[14] However, when molecular analysis was used, level 2B positivity increased to 45%. No instance of isolated metastasis to level 2B lymph nodes without involvement of other nodes was found.

Level 2B node dissection should be considered in histologically positive nodes in the N0 neck, histologically positive nodes in level 2 or 3, primary tumors in the pharynx, extracapsular spread in the lymph node, tongue cancers, tonsillar cancer, skin cancer that drains to level 2, and parotid cancers.

Level 2B involvement in laryngeal cancer in an N0 neck is rare. The prevalence of level 2B metastasis is 1% in the N0 neck. Therefore, level 2B dissection can be avoided in the clinically N0 neck, which in turn prevents postoperative shoulder dysfunction. However, studies have shown that the prevalence of level 2B metastasis in a clinically positive neck is 37%.

Cancer of the head and neck metastasizes in an orderly manner; however, skip metastasis or discontinuous metastasis can occur. The incidence of skip metastasis to level 2 and 3 in oral cancer is 10%. The incidence of metastasis to level 4 lymph nodes in tongue cancer is 15.8%.

Skip metastasis in cancer of the larynx, glossoepiglottic area, and parotid is uncommon.

Management of the neck in sinonasal malignancies deserves special attention. Since these tumors are uncommon compared with other malignancies of the head and neck, the evidence is still limited. In esthesioneuroblastomas, the high regional failure rate in the untreated neck has lead to authors reporting beneficial effects from elective neck dissection for patients with Kadish stage B and C.[15]

It is also recommended to perform elective neck dissection (levels I-III) in patients with T2, T3, or T4 maxillary, palatal alveolar, and gingival SCCA at the time of initial resection.[16]

Management of the N0 neck in patients with advanced T3-T4 SCC of the larynx is still controversial.[17] A 2009 study by Dias et al demonstrated that SND (2-4) might be adequate (97% locoregional control).[18]

The treatment options are as follows:

  • Sentinel lymph node biopsy (SLN): Although supraomohyoid neck dissection is still the criterion standard treatment for the N0 neck, it is currently being evaluated for use in head and neck cancer patients. The accuracy of this technique depends on pathological diagnosis and the method of localization. This can be either through a blue dye, radio-labeled lymphoscintigraphy or a combination of techniques. Hu et al[19] reported on the excision of 3 lymph nodes with the highest radioactive counts for accurate identification of cervical lymph node metastases with clinically N0 necks in laryngeal and hypopharyngeal cancers. The main advantage of SLN biopsy is its decreased morbidity compared with selective neck dissection.[20]

  • If extended supraomohyoid neck dissection (levels 1-4) is performed and if the level 4 is negative based on intraoperative assessment and or frozen section, then the patient can be followed up postoperatively. If level 4 is positive, the options are as follows:

    • Postoperative radiotherapy

    • Convert extended supraomohyoid neck dissection to comprehensive neck dissection (levels 1-5)

    • Comprehensive neck dissection and postoperative radiotherapy

  • Supraomohyoid neck dissection and a sample of level 3 for frozen section: If the lymph node is negative, patient can be closely followed up postoperatively. If lymph node is positive, the options are as follows:

    • Level 4 included in the dissection and postoperative radiotherapy

    • Comprehensive neck dissection (levels 1-5)

    • Comprehensive neck dissection and postoperative radiotherapy

    • Note that extending the operation, with or without postoperative radiotherapy, makes a difference in regard to locoregional control, and survival remains to be seen.

  • Extended supraomohyoid neck dissection (levels 1-4) is performed for oral and tongue cancer.

Postoperative Details

Radiation is indicated following selective neck dissection if 3 or more nodes contain metastases, if extracapsular spread is present, or if a nodal metastasis is found in 2 noncontiguous zones (ie, skip metastases).[21, 22] In patients who meet these criteria, radiation is recommended because it has been shown to significantly decrease the risk of recurrence.

Follow-up

Based on the American Head and Neck Society Practice guidelines, the suggested follow-up schedule is as follows:

  • First year posttreatment - Every 1-3 months

  • Second year posttreatment - every 2-4 months

  • Third year posttreatment - every 3-6 months

  • Fourth year posttreatment - every 4-6 months

  • Fifth year posttreatment - every 12 months

Because the local recurrence occurs within 2 years, standard follow-up of patients with head and neck cancer should be based on the individual patient characteristics.

Life-long follow-up is recommended because of the 20% lifetime risk of developing a second primary tumor.

Studies regarding follow-up have implied that most are aware of significant changes and seek early intervention, making strict routines unnecessary. However, head and neck surgeons (otolaryngologist and general surgeons) currently monitor their patient routinely, regardless of whether the patient has any new reports.

Complications

Complications of prophylactic neck dissection include the following:

  • Postoperative pain

  • Wound infection

  • Hematoma

  • Spinal accessory weakness

Complications of radiation therapy include the following:

  • Xerostomia

  • Neck stiffness

  • Inability to use radiation again in the area

  • Esophageal strictures

Outcome and Prognosis

The overall prognosis of patients with an N0 neck is quite good. Surgery and radiation offer control rates in excess of 95%. However, the prognosis changes if the N0 neck is not truly an N0 neck. Lymph nodes metastases identified with prophylactic neck dissection upstage the patient, and patient survival may decrease by 50%. The primary site and prognostic histologic characteristics affect the survival and should be taken into consideration.

Future and Controversies

Several investigational but promising new methods of early cancer detection are as follows:

  • MRI spectroscopy: This allows for spectroscopic evaluation of a specific tissue area. By measuring levels of choline and creatinine, differentiating tumor from normal tissue is possible because the choline/creatinine ratio is much higher in SCCA.

  • PET-MRI fusion: The anatomic resolution of MRI fused with the metabolic activity of tumor as determined by PET scan is presently being studied to determine its accuracy for head and neck tumors. Its role in the imaging for head and neck cancer remains to be defined.

  • Dynamic MR lymphangiography and carbon dye for sentinel lymph node detection: A Gadomer and carbon dye mixture is injected to the primary site. The sentinel lymph node is identified with MR lymphangiography followed by sentinel lymph node biopsy. MR lymphangiography provides spatial and anatomical localization and the sequence of nodal filling, thus identifying the second echelon lymph nodes without exposure to radioactive tracer. The visual marker (carbon dye) can last for at least a week, and the carbon does not interfere with histologic evaluation of the node. This technique, however, is still experimental.

  • Isosulfan blue/technetium scanning

    • Isosulfan blue and technetium are injected peritumoral or around the tumor. Injection of the blue dye and technetium in the tumor is not recommended since the lymphatic channels in the tumor are destroyed.

    • The sentinel node is detected using a Geiger counter to detect radioactivity, and the blue dye is visualized during lymph node dissection. The consensus of the second conference on sentinel lymph node biopsy in mucosal head and neck cancer recommends use of radiotracer, lymphoscintigraphy, and a hand-held gamma probe for lymphatic mapping as minimal requirements. The use of conventional hematoxylin and eosin staining and cytokeratin is mandatory, and step sectioning of the entire node at intervals of 150 μm is recommended.

    • This method is used routinely for melanomas outside the head and neck, and its application is gaining popularity among head and neck surgeons for detecting metastases from head and neck melanomas. A meta-analysis of 19 articles in the literature on the use sentinel lymph node biopsy in SCCA revealed that the results are reliable and reproducible. Other studies revealed that sentinel lymph biopsy in head and neck cancer is feasible, with a success rate of 90% and a false-negative rate of less than 5%; however, its clinical use in the oral cavity and the oropharynx is still investigational, and trials are in progress to determine its diagnostic efficacy.

  • Sentinel lymph node biopsy using Lymphoseek

    • The perfect agent used in SLN mapping should have high sensitivity of localization, rapid efflux from the tumor site and should selectively target the sentinel nodes. A new agent, Lymphoseek, which is being tested[23, 24] delivers these properties and is stable enough to allow imaging to be performed one day prior to the surgery. It is a dextran-based product that is modified to be labelled with technetium-99 (Tc99). Its small size, with an average of 5 nm, together with its high water solubility allows for enhanced primary site efflux.

    • The product also has long-lasting selectivity for the sentinel nodes by targeting mannose receptors, which are expressed on the abundant dendritic and macrophage cells in the lymph nodes. A US Food and Drug Adminstration-monitored, prospective multi-institution phase 3 trial of Lymphoseek for SLN biopsy in patients with N0 neck with oral cavity squamous cell carcinoma is currently in progress.[3]

  • Photosensitizing drugs used in photodynamic therapy: This has potential use for labeling occult metastases. These drugs remain in the tumor cells longer and fluoresce under black light. Studies are currently underway to assess the diagnostic applications of photodynamic therapy. In patients who undergo prophylactic neck dissection, the fatty lymphatic tissue is examined with a black light, and the areas that fluoresce are sent for pathologic examination to determine if they contain SCCA.

  • Molecular markers for cancer diagnosis are being investigated. These markers and possible clinical applications for cancer diagnosis are as follows:

    • DNA markers

      • TP53 mutation - Detection in saliva; cancer detection in surgical margins

      • Loss of heterozygosity (chromosomes 3p, 9p, 17p, 18q) - Detection in saliva; cancer detection in surgical margins

      • p16 and MGMT methylation - Detection in serum or saliva; cancer detection in surgical margins

      • Clonality analysis by X-chromosome activation - Detection of lymph node metastasis

      • Amplification of chromosome region CCNL1 - Detection of cancer progression and prognosis

    • RNA markers

      • Cytokeratin expression - Detection of lymph node metastasis; detection of disseminated tumor cell

      • E48 antigen expression - Detection of lymph node metastasis; detection of disseminated tumor

      • Pemphigus vulgaris antigen - Detection of lymph node metastasis

      • Expression profiling - Detection of lymph node metastasis and prognosis

    • Protein-based markers

      • Telomerase - Detection in saliva and prognosis

      • Matrix metalloproteinase-9 - Detection in the serum

      • elF4E - Surgical margin analysis

      • Metastasis-associated protein 1 (MTA) - Found to be a useful marker to predict lymphatic metastasis in tonsillar cancer[25]

The clinician should bear in mind that the most effective treatment of cancer is to treat the cancer in its earliest stage (when its tumor burden is lowest and when the lymphatic spread is least).