Volume 6 Issue 3 - Australasian Society for Ultrasound in Medicine

Ultrasound evaluation of neck lymph nodes
echogenicity of the lymph nodes may help the
differentiation, as metastatic nodes from medullary
carcinoma of the thyroid are hypoechoic, whereas metastatic
nodes from papillary carcinoma of the thyroid are
hyperechoic. The relatively high incidence of calcification
in metastatic nodes from papillary carcinoma of the thyroid
makes this feature useful for the diagnosis.
Calcification may also be found in lymph nodes, including
lymphomatous and tuberculous nodes, after treatment.
However, the calcification in these nodes is usually dense
and shows acoustic shadowing.
Intranodal necrosis
Lymph nodes with intranodal necrosis, regardless of their
size, are pathologic 4 . Intranodal necrosis can be classified
into two types: cystic necrosis (also known as liquefaction
necrosis) and coagulation necrosis. Cystic necrosis appears
as an echolucent area within the lymph nodes (Figure 10),
whilst coagulation necrosis is an uncommon sign and
appears as an echogenic focus within the nodes 30-32 .
Figure 11 Transverse sonogram of a tuberculous node (arrows).
Note the adjacent soft tissues edema which appears
heterogeneous and hypoechoic with loss of fascial planes
(arrowheads).
Figure 10 Transverse sonogram showing a metastatic node
with intranodal cystic necrosis (arrows).
Intranodal necrosis may be found in malignant and
inflammatory nodes, with cystic necrosis more common
than coagulation necrosis. Cystic necrosis is common in
tuberculous nodes 20, 21 , and metastatic nodes from squamous
cell carcinomas 4 and papillary carcinoma of the thyroid 4, 37 .
Lymphomatous nodes seldom show cystic necrosis unless
the patient has previous radiation therapy or chemotherapy,
or has advanced disease 5, 40 .
Adjacent soft tissues edema
Granulomatous and metastatic nodes can invade the
surrounding soft tissues and cause edema or induration 20, 40 .
On ultrasound, the soft tissues edema is identified by diffuse
hypoechogenicity with loss of fascial planes (Figure 11). It
has been reported that adjacent soft tissues edema is
common in tuberculous lymphadenitis (43% - 49%) 20, 21 .
Therefore, it is a useful feature for diagnosing tuberculosis.
However, soft tissue edema may also be found in patients
with previous radiation therapy of the neck 25 .
Matting
Matting is considered as clumps of multiple abnormal nodes
with no normal intervening soft tissues (Figure 12), and it is
Figure 12 Sonogram showing matting of multiple tuberculous
nodes.
a common feature in tuberculous lymphadenitis (59% -
64%) 20, 21 . The high incidence of matting in tuberculous nodes
is considered to be the result of periadenitis and adjacent
soft tissues edema. Since matting of lymph nodes is common
in tuberculous lymphadenitis, it is a useful feature to
differentiate tuberculosis from other diseases.
Vascular pattern
It has been reported that the evaluation of the vascular
pattern of normal and abnormal cervical lymph nodes is
highly reliable, with a repeatability of 85% 41 . Small normal
lymph nodes (maximum transverse diameter < 5 mm)
usually do not show vascular signals as the blood vessels
are too small to be detected. Approximately 90% of normal
lymph nodes with a maximum transverse diameter greater
than 5 mm present with hilar vascularity 33 . Normal and
reactive lymph nodes usually present with hilar vascularity,
or may seem to be apparently avascular 42-45 .
Peripheral or mixed vascularity are common in metastatic
nodes 42-44, 46, 47 . Therefore, the presence of peripheral vessels
in lymph nodes is highly suspicious of malignancy. The
peripheral vascularity in metastatic nodes is related to
tumour infiltration of the lymph nodes in which the tumour
14 ASUM ULTRASOUND BULLETIN VOLUME 6 NUMBER 3 AUGUST 2003