Thyroid nodule echocardiography or ultrasound
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Risk calculators and risk factors for Thyroid nodule echocardiography or ultrasound |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Ultrasound
Thyroid nodule assessment
Thyroid gland ultrasound is one of the first steps and the image modality of choice in thyroid nodule diagnostic evaluation. In the case of multiple nodules presentation, all the nodules should be assessed for suspicious ultrasound characteristics. The important points in ultrasound evaluation include:
- Confirmation of the diagnosis of a thyroid nodule
- Assess the size of the nodule
- Determining the location of the nodule
- Determination of the shape of the nodule
- Evaluation of the composition
- Evaluation of the echogenicity
- Evaluation of the margins
- Presence of calcification
- Evaluation of the vascularity of the nodules
- Evaluation of the adjacent structures in the neck including the lymph nodes
- FNA decision making
- Based on the size, vascularity, and shape
The following characteristics are associated with a higher likelihood of malignancy:
- Shape that is taller than wide measured in the transverse dimension
- Hypoechogenicity
- Irregular infiltrative margins
- Microcalcifications
- Absent halo
- Increased intranodular vascularity
The following characteristics are more likely to be a benign lesion:
Spongiform appearance (99.7 % specific for benign thyroid nodule)[2]
Papillary and Follicular tumor differentiation based on ultrasound features
General sonographic appearances of papillary and follicular thyroid cancer can be differentiated from each other.
- A PTC is generally solid or predominantly solid and hypoechoic, often with infiltrative irregular margins and increased nodular vascularity. Microcalcifications, if present, are highly specific for PTC, but may be difficult to distinguish from colloid.
- Conversely, follicular cancer is more often iso- to hyperechoic and has a thick and irregular halo, but does not have microcalcifications. Follicular cancers that are <2 cm in diameter have not been shown to be associated with metastatic disease
- A pure cystic nodule, although rare (<2% of all nodules), is highly unlikely to be malignant.
- A spongiform appearance, defined as an aggregation of multiple microcystic components in more than 50% of the nodule volume, is greately specific for identification of a benign
Elastography
- Elastography is an emerging and promising sonographic technique:
- Shear wave elastography provides a map of the elasticity in the ndular region and allows to quantify stiffness of the lesions in kilopascals in order to reinforce the predictive value of malignancy. A tumour whose stiffness is greater compared to its surrounding healthy tissue is highly suspicious of malignancy. Shear wave elastography may also enable the earlier detection of malignant follicular tumours that currently escape detection by the ultrasound and fine needle aspirration tdue to inappropriate determination of the location. Lymph node metastasis of papillary thyroid cancer can also be detected by elastography due to its increased stiffness.
- a higher intensity pulse is transmitted to produce shear waves, which extend laterally from the insonated structure. The shear waves may then be tracked with low intensity pulses to find the shear velocity
[3] It is recommended that serial US be used in follow-up of thyroid nodules to detect clinically significant changes in size, Since the accuracy of physical examination for nodule size is likely inferior to that of US
[4] There is no consensus on the definition of nodule growth based on US, however, or the threshold that would require rebiopsy
A 50% cutoff for nodule volume reduction or growth, which is used in many studies, appears to appropriate and safe, since the false-negative rate for malignant thyroid nodules on repeat FNA is low
FNA Criteria Based On Ultrasound
| Solitary thyroid nodule | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Cystic nodule | Spongiform nodule | Solid nodule | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Without malignant features | Hyperechoic or isoechoic or partially cystic nodule with eccentric solid areas | Hypoechoic solid nodule with smooth margins WITHOUT the following features: Microcalcifications Extrathyroidal extension Taller than wider shape | Hypoechoic solid nodule or solid hypoechoic component of a partially cystic nodule WITH one or more of the following features: Irregular margins Microcalcifications Taller than wide shape Rim calcifications with small extrusive soft tissue component Evidence of extrathyroidal extension | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Very low suspicion of malignncy | Low suspicion for malignancy | Intermediate suspicion of malignancy | High suspicion of malignancy | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Estimated risk of malignancy <3% | Estimated risk of malignancy 5 to 10% | Estimated risk of malignancy 10 to 20% | Estimated risk of malignancy >70 to 90% | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| FNA if nodule is larger that 2cm | FNA if nodule is larger that 1.5cm | FNA if nodule is larger that 1cm | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Cervical lymph node assessment
The most important nodules that should be evaluated in a patient with thyroid nodule include anterior, central and lateral compartment cervical nodules. During sevical lymph node assessment, the following characteristic should have FNA evaluation for cytology and washout Tg measurement:
- Microcalcification withing the lymph node
- Cystic lymph nodes
- Peripheral vascularity
- Hyperechogenicity of the lymph node
- Round shape lymph node
Lymph node characteristics that are associated with a higher likelihood of abnormal metastatic lymph nodes :
- Loss of the fatty hilus
- The most sensitive characteristic for detecting abnormal metastasis (100%sensitive)
- a low specificity of only 29%
- A rounded rather than oval shape
- Hypoechogenicity
- Cystic change
- Calcifications
- Peripheral vascularity No single sonographic feature is adequately sensitive for detection of lymph nodes with metastatic thyroid cancer (ATA)
Malignant lymph nodes are much more likely to occur in levels III, IV, and VI than in level II Confirmation of malignancy in lymph nodes with a suspicious sonographic appearance is achieved by US-guided FNA aspiration for cytology and=or measurement of Tg in the needle washout. 12491509 16434461 <<lymph node metastasis picture explanation>> Lymph node compartments separated into levels and sublevels. Level VI contains the thyroid gland, and the adjacent nodes bordered superiorly by the hyoid bone, inferiorly by the innominate (brachiocephalic) artery, and laterally on each side by the carotid sheaths. The level II, III, and IV nodes are arrayed along the jugular veins on each side, bordered anteromedially by level VI and laterally by the posterior border of the sternocleidomastoid muscle. The level III nodes are bounded superiorly by the level of the hyoid bone, and inferiorly by the cricoid cartilage; levels II and IV are above and below level III, respectively. The level I node compartment includes the submental and submandibular nodes, above the hyoid bone, and anterior to the posterior edge of the submandibular gland. Finally, the level V nodes are in the posterior triangle, lateral to the lateral edge of the sternocleidomastoid muscle. Levels I, II, and V can be further subdivided as noted in the figure. The inferior extent of level VI is defined as the suprasternal notch. Many authors also include the pretracheal and paratracheal superior mediastinal lymph nodes above the level of the innominate artery (sometimes referred to as level VII) in central neck dissection Preoperative neck US for the contralateral lobe and cervical (central and especially lateral neck compartments) lymph nodes is recommended for all patients undergoing thyroidectomy for malignant cytologic findings on biopsy. USguided FNA of sonographically suspicious lymph nodes should be performed to confirm malignancy
References
- ↑ Frates MC, Benson CB, Doubilet PM, Kunreuther E, Contreras M, Cibas ES, Orcutt J, Moore FD, Larsen PR, Marqusee E, Alexander EK (2006). "Prevalence and distribution of carcinoma in patients with solitary and multiple thyroid nodules on sonography". J. Clin. Endocrinol. Metab. 91 (9): 3411–7. doi:10.1210/jc.2006-0690. PMID 16835280.
- ↑ Moon WJ, Jung SL, Lee JH, Na DG, Baek JH, Lee YH, Kim J, Kim HS, Byun JS, Lee DH (2008). "Benign and malignant thyroid nodules: US differentiation--multicenter retrospective study". Radiology. 247 (3): 762–70. doi:10.1148/radiol.2473070944. PMID 18403624.
- ↑ Monpeyssen H, Tramalloni J, Poirée S, Hélénon O, Correas JM (2013). "Elastography of the thyroid". Diagn Interv Imaging. 94 (5): 535–44. doi:10.1016/j.diii.2013.01.023. PMID 23623210.
- ↑ Tan GH, Gharib H, Reading CC (1995). "Solitary thyroid nodule. Comparison between palpation and ultrasonography". Arch. Intern. Med. 155 (22): 2418–23. PMID 7503600.
- ↑ Brauer VF, Eder P, Miehle K, Wiesner TD, Hasenclever H, Paschke R (2005). "Interobserver variation for ultrasound determination of thyroid nodule volumes". Thyroid. 15 (10): 1169–75. doi:10.1089/thy.2005.15.1169. PMID 16279851.