Cervical ultrasound is the method of choice for the identification of lymph node metastases.
Ultrasound can detect lesions as small as 4mm,
and increased 50% in detecting recurrences smaller than 1cm1,2.
Also proves to be useful in the evaluation of the cervical internal architecture and can even be combined with fine needle aspiration biopsy,
allowing a single examination,
the primary tumor and cervical metastases be evaluated.3,4,5,6
Differentiated malignant thyroid tumors have good prognosis,
unlike medullary and anaplastic carcinomas.
However,
5 - 40 % of patients have persistent or recurrent disease,
most often in the lymph nodes on the central compartment ipsilateral side but also in the remaining thyroid tissue or contralateral lymph nodes.4,7,8
Papillary thyroid carcinoma has a high propensity for invasion of cervical lymph nodes,
the incidence ranges from 30 to 90%,
being higher in systematic surgery with excision of the cervical lymph nodes.
Medullary carcinoma (50%) and anaplastic carcinoma (40%) also have a high tendency to invade lymph nodes,
while the less common follicular carcinomas (10%).9,10
Normal cervical nodes,
usually show hilar vascularity or appear apparently avascular.
Metastatic lymph nodes are usually round in shape,
without an echogenic hilus.
The majority of metastatic nodes appear hypoechoic.
Cystic necrosis is common in metastatic nodes from squamous cell carcinomas,
and papillary carcinoma,
and papillary carcinoma of the thyroid.
Intranodal calcification is a characteristic feature in metastases from papillary carcinoma of thyroid.
On ultrasound,
intranodal calcification appears as an echogenic focus with or without acoustic shadowing.
Although metastases cause enlargement of lymph nodes,
nodal size is not an accurate criterion in identifying metastatic nodes because micro-metastases may be found in small lymph nodes,
and inflammation may cause nodal enlargement.9,11
Therefore,
precise diagnosis for the presence of lymph nodes metastases (LNM) is important.
Imaging of lymph nodes plays an important role in determining surgical procedures because physical examination is less accurate for detecting cervical lymph nodes.
15,16,17,18,19,20.
High-resolution cervical lymph nodes ultrasonography has emerged as an important tool in evaluating locoregional recurrence.
The sensitivity for lymph nodes sonogram in detecting cervical disease ranges from 70 a 100%.
21