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Year : 2000  |  Volume : 10  |  Issue : 1  |  Page : 25-28
Pictorial essay: Sonographic patterns of cervical nodal disease in papillary thyroid carcinoma


Dept of Radiology, INHS Asvini, Coloba, Mumbai 400 005, India

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Keywords: Cervical nodes, Metastasis, hyroid malignancy

How to cite this article:
Ganesan S. Pictorial essay: Sonographic patterns of cervical nodal disease in papillary thyroid carcinoma. Indian J Radiol Imaging 2000;10:25-8

How to cite this URL:
Ganesan S. Pictorial essay: Sonographic patterns of cervical nodal disease in papillary thyroid carcinoma. Indian J Radiol Imaging [serial online] 2000 [cited 2019 Sep 20];10:25-8. Available from: http://www.ijri.org/text.asp?2000/10/1/25/30627
Papillary carcinoma of the thyroid (PCT) is the commonest malignant tumor of the thyroid with a peak incidence between the third and the fifth decades. Histologically, PCTs range from a predominantly papillary pattern to those that in some part are follicular, with most of the lesions having a mixed architecture histologically, with equal parts of papillary and follicular components [1]. PCTs have a high propensity for invading the lymphatics, including those within the gland, presenting as multifocal lesions. Fifty to sixty percent of patients have cervical metastatic nodes at the time of initial clinical presentation [1],[2]. Even though various territories of the thyroid drain into different groups of nodes, dissemination may occur in any direction through the freely communicating rich plexus of lymphatics within the gland. Nodes are confined to ipsilateral level III and IV groups of nodes and also to the prelaryngeal and paratracheal groups. Contralateral nodal involvement is uncommon [1],[2]. Metastatic nodes from PCT present as a predominantly hypoechoic pattern. A homogeneous hypoechoic pattern is noted in the absence of microcalcifications due to Psammoma bodies or consequent to cystic degeneration. Hemorrhage into a node may present as a fluid-debris level. Evidence of extranodal spread into soft tissues, internal jugular vein or carotid artery involvement may be observed.


   Pathological Considerations Top


The incidence of thyroid malignancies is steadily increasing over the decades. Thyroid malignancies are two to three times more common in females, this female preponderance disappearing before puberty and after menopause. This is possibly explained by the fact that most well differentiated thyroid carcinomas have estrogen receptors. Morphologically 75 - 85% of thyroid malignancies are of the papillary type, follicular and medullary patterns constituting 10-20% and 5% respectively. Anaplastic carcinoma is extremely rare. Lymphomas and other mesenchymal tumors constitute a miniscule percentage. Various studies have shown a genetic predisposition to PCT. It has been observed that all PCTs are monoclonal and in addition a new oncogene named PCT oncogene has been identified in 30% of these lesions [1],[2]. Previous radiation to the neck and thyroid diseases such as Hashimoto's disease and possibly multinodular goiter are known to act as predisposing factors. Diffuse hyperplasia and adenomas are not implicated as a predisposing factor to the development of thyroid carcinoma [1].

PCT lesions range in size from a few millimeters to 7-10cms. They are rarely encapsulated and infiltrate the thyroid parenchyma diffusely. Extension into perithyroidal soft tissues is not common. PCTs have a high propensity to invade the lymphatics. Spread along the lymphatics within the gland is responsible for the multifocal lesions very often seen in PCT. More than 60% patients have cervical nodal disease at the time of initial presentation. Distant metastases are rare [1],[2].

Histologically these lesions range from a predominantly papillary pattern to those that are follicular in some parts with most of the lesions having a mixed architecture with almost equal papillary and follicular components. Whatever the architecture, all patterns of PCT behave biologically in a similar manner. Psammoma bodies within the cores of the papillae surrounded by calcific lamellations are the hallmark of PCTs and are considered diagnostic of PCT. Areas of cystic degeneration ranging from a few millimeters to grossly cystic lesions may be present [1],[2],[3].

Cervical lymph nodal metastases are observed in 60% of patients at the time of initial presentation. Metastatic nodes demonstrate pathological changes identical to those of the primary lesions in thyroid. Demonstration of Psammoma bodies in a lymph node is specific and diagnostic of PCT. Focal areas of cystic degeneration to totally cystic patterns similar to the primary lesions may be seen in the nodes as well [1],[2],[3].


   Sonographic Observations Top


Cervical lymph nodes are present in 15-20% of thyroid malignancies and in 50-60% of PCTs at the time of initial presentation. Different territories of thyroid drain into different groups of nodes; the upper part of the thyroid drains directly as well as through the prelaryngeal nodes into the upper deep cervical nodes along the middle third of internal jugular vein (level III nodes). The lower part of the gland drains directly into the lower deep cervical nodes, along the internal jugular vein (level IV nodes) and also to the pre and para-tracheal groups of nodes. Lymph can pass in any direction through the freely communicating plexus within the thyroid. Nodes are usually confined to the ipsilateral side and contralateral nodal involvement is extremely rare in PCTs [1],[2],[4].

Metastatic nodes in PCTs vary in number from three to five, the group adjacent to the thyroid in the thyroid bed region often appearing continuous with the gland. Nodes are round in shape with roundness index well below 1.5, the axial diameter approaching longitudinal measurements. Nodal size is variable. The nodal capsule is well defined and a distinct echogenic capsule [2],[3],[5],[6] separates adjacent nodes.

Involved nodes present a predominantly hypoechoic pattern compared to the normal thyroid parenchyma and the adjacent muscle. A homogeneous fleshy pattern is commonly observed in the absence of microcalcifications or cystic degeneration. Hilar echoes are usually absent, however their presence does not rule out metastatic involvement. Microcalcifications less than 2mms in size are seen as 'dots' or in small clusters with or without distal shadowing and represent calcified Psammoma bodies that are detected in metastatic nodes from PCT. These microcalcifications are not specific to metastases from PCT even though they serve as excellent sensitive markers for suggesting the diagnosis [2],[3],[6],[7],[9] [Figure - 1],[Figure - 2],[Figure - 3].

Small, solitary or multiple anechoic areas representing cystic degeneration may be observed in metastatic nodes from PCT. In certain cases, cystic changes may be so pronounced that the entire node appears totally cystic, limited only by the echogenic capsule peripherally. Hemorrhage into a cystic node presenting as fluid levels may be observed in lymph nodes and is considered virtually diagnostic of PCT metastases [2],[8] [Figure - 4],[Figure - 5],[Figure - 6],[Figure - 7].

Extranodal spread involving muscles, perinodal soft tissues, carotid artery and internal jugular vein (IJV) as well as neural involvement may be observed in some cases. These changes may be due to primary tumor, metastatic nodes or both. Nodal encasing of the ICA may be present. IJV involvement may range from simple compression and displacement to total occlusion secondary to thrombus formation. Thrombus formation can extend proximally for a variable length. Sonologically, these findings manifest as intraluminal echogenic filling defects in IJV to total non-visualization. Doppler studies will show flow changes depending upon the degree of obstruction [2],[10] [Figure - 8],[Figure - 9]. IJV compression and occlusion due to thrombus formation are more common than direct ICA involvement.

High frequency, high resolution ultrasound plays an important role in the evaluation of cervical lymph nodes. Ultrasound is a highly sensitive technique for detecting enlarged cervical lymph nodes even when they are not palpable. The distribution pattern of enlarged nodes, presence of focal microcalcifications in spotty or cluster distribution, areas of cystic degeneration and the presence of similar appearing solitary or multiple focal thyroid lesions are highly suggestive of papillary thyroid carcinoma. Microcalcifications and cystic degeneration even though established as a reliable sign of thyroid malignancy, are non-specific. Similar findings have been observed in metastatic nodes from squamous cell carcinoma. Tuberculous nodes can be differentiated easily in view of the coarseness of the macro-calcifications, central caseation, matting, perinodal collection, long, continuous, chain-like distribution pattern and associated peripheral fibrous reaction. Ultrasound also plays a major role in the evaluation of patients with PCT after surgery and radiotherapy in detecting non-functioning recurrences either in the thyroid bed or in the lymph nodes [2],[5].

 
   References Top

1.Cotran RS, Kumar V, Robbins SL. Thyroid gland, malignant tumors, in pathologic basis of disease. 5th ed. USA: WB Saunders and Co, 1136-1142.  Back to cited text no. 1    
2.Solbiati L, Croce F. Thyroid and parathyroid, abdominal and general ultrasound. Vol. 2 edited by Cosgrove et al . London: Churchill Livingstone, 1993; 661-671.  Back to cited text no. 2    
3.Solbiati L, Bellarati E, Cioffi V, et al . Microcalcifications: A clue in the diagnosis of thyroid malignancies. Proceedings of 76th RSNA, Chicago 1990; 140.  Back to cited text no. 3    
4.Sakai F, Kiyomo K, Sone S, et al . Ultrasonic evaluation of cervical metastatic lymphadenopathy. J Ultrasound Med 1988; 7: 305.  Back to cited text no. 4    
5.James EM, Charboneau JW, Hay ID. The thyroid, diagnostic ultrasound edited by Rumack RM et al . St. Louis: Mosby Year, 1991; 507-523.  Back to cited text no. 5    
6.Solbiati L, Rizatto L, Belloti F et al . High resolution sonography of cervical lymph nodes in head and neck cancer; criteria for differentiating reactive versus malignant nodes. Proceedings of 74th RSNA, Chicago, 1998; 113.  Back to cited text no. 6    
7.Marchal G, Oyen R, Vershakelen J et al . Sonographic appearance of normal lymph nodes. J Ultrasound Med 1985; 4: 417-419.  Back to cited text no. 7    
8.Hammer M, wortsman J, Folse R. Cancer in cystic lesions of thyroid. Arch Surg 1982; 117: 1020-1023.  Back to cited text no. 8  [PUBMED]  
9.Solbiati L, Volteran L, Rizatto G et al . The thyroid gland with low uptake lesions; evaluation with ultrasound. Radiology 1985; 155: 187-191.  Back to cited text no. 9    
10.Gritzman N, Grasl MCH, Helmer M, Steiner E. Invasion of carotid artery and jugular veinby lymph node metastasis; Detection with sonography. AJR 1990; 154: 441.   Back to cited text no. 10    

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Correspondence Address:
S Ganesan
Dept of Radiology, INHS Asvini, Coloba, Mumbai 400 005
India
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Source of Support: None, Conflict of Interest: None


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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9]



 

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