features for diagnosis of cervical lymphadenopathy
Normal cervical lymph nodes are usually found in submandibular,
parotid, upper cervical and posterior triangle regions. Metastatic
cervical lymph nodes are site-specific. In patients with a known
primary tumour, the distribution of metastatic nodes helps to
identify metastases and assists tumour staging. However, if the
primary tumour is not identified, the distribution of proven metastatic
nodes may give a clue to identify the primary. Specific distribution
is also found in lymphomatous and tuberculous nodes (Table 2).
Table 2. Common sites of metastatic, lymphomatous and tuberculous
nodes in the neck
||Commonly involved nodal groups
|Metastases from oropharynx, hypopharynx, larynx
||Internal jugular chain
|Metastases from oral cavity carcinomas
|Metastases from nasopharyngeal carcinoma
|Metastases from papillary carcinoma of the thyroid
||Internal jugular chain
|Metastases from non-head and neck carcinoma
Malignant nodes tend to be large. However, inflammatory nodes can be as large as malignant nodes. Moreover, metastatic deposit can be found in small nodes. Therefore, size of lymph nodes cannot be used as the sole criterion in differential diagnosis. However, in clinical practice, size of lymph nodes is useful when there is an increase in nodal size on serial examinations in a patient with known primary tumour, which is highly suggestive for metastases. Also, serial change in size of malignant nodes is useful in monitoring patients? response to treatment.
Malignant and tuberculous nodes are usually round in shape with
a short axis to long axis (S/L) ratio greater than or equal to
0.5, whereas reactive and normal nodes are usually long or oval-shaped.
Nevertheless, it has been reported that normal submandibular and
parotid nodes tend to be round in shape. Moreover, malignant nodes
may be oval in shape when they are in early stage of involvement.
Therefore, nodal shape should be considered as the sole criterion
in the diagnosis. However, eccentric cortical hypertrophy, which
indicates focal intranodal tumour infiltration, is a useful sign
to identify malignant nodes.
Metastatic and lymphomatous nodes tend to have sharp borders, whereas reactive and normal nodes usually show unsharp borders . The sharp borders in malignant nodes are believed to be due to the tumour infiltration and the reduced fatty deposition within the lymph nodes which increase the acoustic impedance difference between the lymph node and the surrounding tissues. Unsharp borders are common in tuberculous nodes and these are due to the edema and inflammation of the surrounding soft tissue (periadenitis). In our experience, border sharpness is not helpful in differential diagnosis. However, in clinical practice, a proven malignant node with unsharp borders indicates extracapsular spread, which helps in the assessment of patient prognosis.
Echogenic hilus is a normal sonographic feature
of most of the normal cervical lymph nodes (86%), and it is commonly
seen in larger nodes [8, 9]. On ultrasound, echogenic hilus is
appeared to be continuous with the adjacent soft tissues. Although
metastatic, lymphomatous and tuberculous nodes tend to have absent
hilus, they may present with an echogenic hilus in their early
stage of involvement in which the medullary sinuses have not been
sufficiently disrupted to eradicate it . Therefore, the presence/absence
of echogenic hilus should not be the sole criterion in the diagnosis.
Normal, reactive, lymphomatous and tuberculous
nodes are predominantly hypoechoic when compared with the adjacent
muscles. Metastatic nodes are usually hypoechoic, except for metastases
from papillary carcinoma of the thyroid which tend to be hyperechoic
. Therefore, hypereechogenicity is a useful sign to identify
metastatic nodes from papillary carcinoma of the thyroid. Radiologist
should scan the thyroid for a primary tumour if hyperechoic nodes
Lymphomatous nodes were previously reported to have a pseudocystic appearance, i.e. hypoechoic with posterior enhancement [12, 13]. With the use of newer transducer, lymphomatous nodes are less likely to have the pseudocystic appearance, whereas they demonstrate a micronodular appearance .
Intranodal calcification is rarely found in cervical
lymphadenopathy. However, about 50-69% of metastatic nodes from
papillary carcinoma of the thyroid show calcification which is
punctuate, peripherally located and may show acoustic shadowing
with a high-frequency transducer [11, 15]. Therefore, the presence
of characteristic calcification is a useful feature to identify
metastatic nodes from papillary carcinoma of the thyroid.
Intranodal calcification may be found in lymphomatous
and tuberculous nodes after treatment but the calcification is
usually dense and shows acoustic shadowing.
Lymph nodes with intranodal necrosis are considered
to be pathologic. Intranodal necrosis can be classified into coagulation
necrosis and cystic necrosis, where cystic necrosis is more common
than coagulation necrosis. Coagulation necrosis appears as an
intranodal echogenic focus, whilst cystic necrosis appears as
an echolucent area within the lymph nodes. Cystic necrosis is
commonly found in tuberculous nodes and metastatic nodes from
squamous cell carcinomas and papillary carcinoma of the thyroid.
Ancillary features that help in the evaluation
of cervical lymphadenopathy are adjacent soft tissues edema and
matting. On ultrasound, soft tissues edema appears as an diffuse
hypoechogenic area with loss of fascial planes, whereas matting
is clumps of multiple abnormal lymph nodes with abnormal intervening
soft tissues. Adjacent soft tissues edema and matting are common
features in tuberculous nodes, whilst these features are relatively
less common in metastatic and lymphomatous nodes . The high
incidence of adjacent soft tissues edema and matting in tubeculous
nodes is believed to be due to the perinodal inflammatory reaction
(periadenitis) of the nodes. However, one should note that adjacent
soft tissues edema and matting may be found in patients with previous
radiation treatment on the neck .
Normal and reactive lymph nodes tend to have hilar
vascularity or appear apparently avascular, whereas metastatic
nodes usually show peripheral or mixed vascularity, and lymphomatous
nodes predominantly demonstrate mixed vascularity [17, 18]. As
peripheral vascularity is not found in normal or reactive nodes,
the presence of peripheral vascularity, regardless of sole peripheral
or mixed vascularity, is highly suspicious of malignancy.
On ultrasound, tuberculous nodes have varied vascular
pattern, which simulates both benign and malignant conditions
[17, 19]. In spite of the varied vascular pattern, displaced vascularity
and apparent avascularity are common in tuberculous nodes, which
are related to the high incidence of cystic necrosis in tuberculous
lymph nodes [17, 19].
In the evaluation of the vascular resistance (RI and PI) of cervical lymph nodes, the mean, highest and lowest values have been reported [20-22]. However, we found that the repeatability of measurement is higher when the mean value is used .
The role of RI and PI in distinguishing malignant and benign nodes is controversial. It has been reported the metastatic nodes have a higher RI and PI than reactive nodes [21, 24]. However, another study found that there was no significant difference in RI and PI between benign and malignant nodes . Our studies found that metastatic nodes tend to have a higher RI and PI than reactive nodes, except for the metastatic nodes from papillary carcinoma of the thyroid which show similar RI and PI with reactive nodes [17, 26]. Nevertheless, we found that the combination of grey scale sonographic features and vascular pattern of lymph nodes already have a high accuracy in differentiating metastatic and reactive nodes . Therefore, measurement of the vascular resistance of lymph nodes may not be necessary in routine clinical practice.