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Discussion Diagnostic approach of mediastinal masses on image
Thymoma v.s. Bronchogenic cyst Other methods of diagnostic radiology Thoracic Radiology THE REQUISITES Ch 15~16 Eur. Radiol. 8, (1998)
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Diagnostic approach of mediastinal masses on image
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The 4 D’s of mediastinal masses
Detection: mediastinal landmarks Lines Stripes Interfaces Descriptive features of mediastinal masses Intimate effect on mediastinal structures Smooth, sharp margins Obtuse angles with adjacent lung Division of the mediastinum Differential diagnosis
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Detection: mediastinal landmarks
Lines Anterior junction line Posterior junction line Right and left paraspinal lines Stripes Right paratracheal stripe Interfaces Azygoesophageal interface Descending aortic interface
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Anterior and posterior junction lines
Detection of a displaced junction line allows both identification of a mediastinal abnormality and localization as either anterior or posterior
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Anterior and posterior junction lines
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Right and left paraspinal lines
Displacement of the left paraspinal line lateral to the descending aortic interface signals the presence of a posterior mediastinal abnormality An ectatic aorta may displace the left paraspinal line laterally Lymphoma
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Right paratracheal stripe
Lymphadenopathy It is seen as a smooth stripe of uniform width (<3mm) Widening of the right paratracheal stripe is a sign of middle mediastinal pathology
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Right paratracheal stripe
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Azygoesophageal interface
Bronchogenic cyst A focal convexity of the azygoesophageal interface signals the presence of a mediastinal abnormality
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Descending aortic interface
Abnormalities in the descending aortic interface imply pathology within the posterior mediastinum Descending thoracic aortic aneuryam
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Descriptive features of mediastinal masses
Lung mass Intimate effect on mediastinal structures Dose not usually produce an intimate effect Smooth sharp margins Usually irregular margins Obtuse angles Acute angles
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Descriptive features of mediastinal masses
Thyroid adenoma
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Division of the mediastinum
Anterior mediastinum Boundaries Anteriorly by the sternum Posteriorly by the anterior margins of the pericardium, aorta, and brachiocephalic vessels Normal structures Thymus gland, lymph nodes, fat, internal mammary vessels
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Division of the mediastinum
Middle mediastinum Boundaries Posterior margin of anterior division and anterior margin of posterior Normal structures Heart and pericardium, ascending and transverse aorta, brachiocephalic vessels, SVC and IVC, main pulmonary vessels, trachea and main bronchi, lymph nodes, fat Posterior mediastinum Boundaries Anteriorly by the posterior margins of the pericardium and great vessels Posteriorly by the thoracic vertebral bodies Normal structures Descending thoracic aorta, esophagus, thoracic duct, azygous/hemiazygous, autonomic nerves, lymph nodes, fat
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Differential diagnosis
Anterior mediastinum Thymoma, lymphoma, germ cell neoplasms, thyroid abnormalities Middle mediastinum Lymphadenopathy, bronchogenic cyst, vascular abnormalities, pericardial cyst, tracheal tumor Posterior mediastinum Neurogenic tumors, paravertebral abnormalities, vascular abnormalities, esophageal abnormalities, lymphadenopathy, neurenteric cyst, Bochdalek hernia, extramedullary hematopoeisis
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Thymoma v.s. Bronchogenic cyst
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Thymoma Thymomas are tumors composed of an admixture of thymic epithelial cells and reactive lymphocytes Account for the majority of anterior mediastinal masses in adults and typically occur as incidental findings Associations Myasthenia gravis, hypogammaglobulinemia, red cell aplasia Age Usually 40~60; unusual in patients < 30 Gender Male and females, equally
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Non-invasive thymoma Descriptive features
Round or oval well-circumscribed, soft-tissue density mass growing asymmetrically to one side of the anterior mediastinum Slightly increases with administration of contrast material Calcifications at the periphery of the lesion or throughout its substance, hemorrhage, or necrosis can also be seen Areas of cystic degeneration are common Usually located anterior to the junction of the heart and great vessels Magnetic resonance imaging has a limited role in the evaluation of thymomas vascular and cardiac extension of invasive thymoma is well identified by MRI
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Invasive thymoma Descriptive features
Appears on CT as an irregular ill-defined mass Additional findings of invasion of adjacent mediastinal structures, chest wall invasion, or contiguous spread along pleural surfaces Direct contact and absence of cleavage planes are not strictly reliable criteria to predict invasion Clear delineation of fat planes surrounding a tumor should be interpreted as indicating an absence of extensive local invasion
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Thymoma
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Bronchogenic cyst Bronchogenic cysts are the result of an abnormality in primitive foregut development Have a fibrous capsule, often contain cartilage, smooth muscle, are lined by respiratory epithelium, and contain mucoid material Occur in all three mediastinal compartments, but the middle mediastinum is the most common site Age Often seen in younger patients, but may be detected at any age
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Bronchogenic cyst Gender
Male and females equally Usually occur as an incidental finding, but they occasionally cause symptoms secondary to compression of adjacent structures Infrequently, they may cause symptoms secondary to infection
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Bronchogenic cyst Descriptive features
Subcarinal or right paratracheal locations Well-defined, homogeneous mass with imperceptible wall Fluid or soft-tissue attenuation on CT On rare occasions they show an extremely high density related to a milk of calcium content Curvilinear calcification of the wall is possible At MRI they frequently show a signal intensity higher than that of muscle on T1-weighted images due to their high proteinaceous content The signal intensity on T2-weighted images is very high, suggesting a cystic lesion
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Bronchogenic cyst
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Other methods of diagnostic radiology
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Ultrasonography Transthoracic US is not currently used in mediastinal mass evaluation The major limitation is an inadequate window Useful information can be obtained especially in children in masses abutting the chest wall and in vascular abnormalities May be used to differentiate cystic from solid masses and relate them to surrounding structures Helpful in the evaluation of masses in close proximity to the heart and pericardium, a setting in which an assessment of extracardiac and intracardiac structures may be helpful
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Biopsy A preoperative histological diagnosis is unnecessary if the mass seems reasonably resectable If the mass is clearly invasive and looks unresectable, then a biopsy, either guided by imaging or surgical, is indicated Small, encapsulated, "typical" thymomas are excised for diagnosis and treatment. Large, invasive, "atypical" thymomas are best managed by biopsy to learn the histology of the tumor and to assess its invasive potential
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Thanks for your attention !!
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