Head and Neck Imaging

Lymphadenopathy, head and neck

Neck lymphadenopathy is commonly seen and may be caused by inflammation or tumoral involvement.

Radiological criteria used to diagnose neck lymphadenopathy on CT and MR studies are size and internal structure. A minimum axial diameter more than 10 mm or the presence of central hypodensity, indicating necrosis, are generally accepted criteria of abnormality (Fig. 1). The size criterion is a compromise between sensitivity and specificity. In squamous cell carcinoma head and neck, the most common head and neck aerodigestive malignancy, recently reported results using these criteria yield for CT a sensitivity of about 90% and a specifity of about 40%; the negative predictive value is about 84% and the positive predictive value about 50%. The results with CT are generally slightly better than with MRI.

None of the currently available imaging methods can reliably depict small tumour deposits within nonenlarged lymph nodes, or differentiate reactively enlarged lymph nodes from metastatic lymphadenopathy. This can be overcome by combining ultrasonography with fine needle aspiration cytology (US-FNAC). In necks where no lymphadenopathies can be palpated ('N0-neck') a sensitivity of 73% and specificity of 100% have been reported with this technique, significantly better than can be obtained with CT or MRI. The reliability of US-FNAC is dependent on the experience of the examiner.

Malignant lymphadenopathy may spread through the lymph node capsule; such extracapsular spread implies a worse prognosis. Radiological criteria for capsular penetration are an irregular nodal margin, without clear distinction between the node and the surrounding fat, and thickening of surrounding fibroadipose tissue or muscles (Fig.1). Only major extranodal spread can be detected by imaging.

Invasion of the carotid artery is important to detect, as resectability may become impossible. Carotid wall involvement can be suggested if the artery is surrounded by more than 270 by the tumour. However, sometimes the surgeon can peel the tumour off the vessel even if this sign is positive.

Also, see lymph nodes of the neck organization, level system of lymph node classification.

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Fig.1

Axial contrast-enhanced CT images in a patient with extensive hypopharyngeal squamous cell carcinoma. a. The primary tumour is extending behind the cricoid cartilage (arrows). Right-sided enlarged parajugular lymph node (arrowhead) showing evidence of necrosis. The node compresses and is poorly delineated from the internal jugular vein; at surgery, macroscopic invasion of the vein was found. b. Level of the valleculae. The upper limit of the primary tumour is seen in the left pharyngo-epiglottic fold (single arrowhead). Left-sided, centrally necrotic adenopathy (arrow). On the right side, a nodal mass is present (double arrowhead), poorly delineated from the sternocleidomastoid muscle, carotid artery and internal jugular vein, with infiltration of surrounding fat tissue and slight thickening of overlying platysma muscle: extracapsular spread of tumour.
Lymphadenopathy, head and neck, Fig.1 (a)
Lymphadenopathy, head and neck, Fig.1 (b)