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. |
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Regardless of the type of imaging chosen, cervical lymph nodes must be considered to harbor metastasis if the any of the following criteria are met:
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Node larger than 1 cm (or >1.5 cm in the jugulodigastric area)
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Round node instead of oval
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Internal central or peripheral attenuation suggestive of necrosis
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Poorly defined mass in the lymph node–bearing area
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The combination of ill-defined borders and loss of plane between mass and normal adjacent neck structures
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Retropharyngeal node larger than 1 cm
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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. [4, 5]
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. [6] In another study by Gilbert et al, [7] 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. [8] A study by Lyons et al found that in patients with early stage oral cancer who were classified as N0, a 20% risk for nodal metastases existed when the primary tumor was more than 6 mm thick. [9]
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. [10] 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.
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Levels of metastasis to cervical lymph nodes.
Tables
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. |
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