Volume 6 Issue 3 - Australasian Society for Ultrasound in Medicine

Ultrasound of salivary glands
Approximately 90% arise from the superficial lobe and are
adequately assessed by ultrasound alone. In about 25% of
pleomorphic adenomas there are associated small satellite
nodules away from the main tumour 16 . Malignant
transformation and calcification are known to occur in long
standing tumour 17 . Recurrence rate varies between 1% and
50% 18 .
On ultrasound this tumour appears as a homogeneous,
hypoechoic solid mass, usually less than 3cm in size (Figure
5). It is round or oval in shape and well-defined with
lobulated margins. Quite often there is posterior acoustic
enhancement. Lesions larger than 3cm are more prone to
cystic or haemorrhagic degeneration which modify the
internal architecture and may also exhibit ill-defined edges,
thus making differentiation from a malignant lesion difficult.
Calcification may also occur in longstanding tumour.
Figure 4 Transverse gray scale sonogram of the right
submandibular gland showing glandular enlargement with
lobulated outline and ‘cirrhotic-like’ echopattern. These
features represent chronic sclerosing sialadenitis (Kuttner
tumour).
Salivary gland neoplasms
Patients with salivary gland tumour usually present with a
palpable lump. In evaluating a focal mass in a salivary gland,
the first step is to identify if the mass is intraglandular or
extraglandular. Up to 20% of clinically diagnosed salivary
gland masses are found by ultrasound to be due to lesions
outside the salivary gland 13 . For a parotid lesion, it is
important to determine its deep lobe involvement, as the
surgical approach would be different. In cases of extensive
deep parotid lobe involvement, extra-parotid components
such as parapharyngeal space extension, ultrasound alone
is insufficient to assess the full tumour extent. Cross-sectional
imaging with computed tomography (CT) or magnetic
resonance imaging (MRI) is necessary in these circumstances.
Once it is established that the neoplasm is intra-glandular
in origin, the next step is to determine its nature, i.e. benign
or malignant. The ultrasound distinction of benign and
malignant lesions is not precise, but certain features should
raise suspicion for malignancy. These include: if the margin
of the lesion is ill-defined or is locally invasive, if the mass is
in the deep lobe, and if abnormal cervical lymph nodes are
present. Ultrasound is able to diagnose a benign lesion in
over 80% of cases 14 . Colour Doppler may help in diagnosing
malignancy when there is disorganized internal colour flow.
The accuracy can be further enhanced by FNAC under
ultrasound guidance, particularly with the help of an
experienced cytopathologist 15 .
Benign neoplasms
1. Pleomorphic adenoma
Pleomorphic adenoma is the most common (60-80%) of the
parotid neoplasms. Women are more commonly affected
than men and patients are usually greater than 40 years of
age at the time of diagnosis. It is ten times more common in
the parotid gland than in submandibular gland.
Figure 5 Transverse gray scale sonogram showing a welldefined,
round, homogeneous, hypoechoic lesion in the left
submandibular gland. These features suggest a benign salivary
gland lesion. Note the posterior acoustic enhancement
commonly seen with pleomorphic adenoma.
The colour Doppler pattern of pleomorphic adenoma is
variable but commonly shows increased peripheral vessels,
mainly venous in nature 19 .
2. Warthin’s tumour (adenolymphoma)
Warthin’s tumour account for 6-10% of all salivary gland
neoplasms. It is more common in elderly men than women.
The apex of the superficial lobe of parotid gland is the
commonest site of involvement. About 15-30% are bilateral.
On ultrasound, a Warthin’s tumour is typically a welldefined
hypoechoic lesion with internal heterogeneity of
solid and cystic areas (Figure 6). It may also appear anechoic
with through transmission. Colour flow Doppler may show
vessels in a hilar distribution.
3. Others
Other benign neoplasms such as lipoma (Figure 7),
oncocytoma and haemangioma are less commonly seen.
Malignant neoplasms
Malignant epithelial tumours of salivary gland account for
17% of all epithelial tumours. The smaller salivary glands
have greater malignant potential, a tumour in the sublingual
or submandibular gland being more likely to be malignant
than a tumour in the parotid gland. Ultrasound alone may
20 ASUM ULTRASOUND BULLETIN VOLUME 6 NUMBER 3 AUGUST 2003