Discussion

1. 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, 1148-1159 (1998)

2. Diagnostic approach of mediastinal masses on image

3. 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

4. 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

5. 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

6. Anterior and posterior junction lines

7. 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

8. 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

9. Right paratracheal stripe

10. Azygoesophageal interface • A focal convexity of the azygoesophageal interface signals the presence of a mediastinal abnormality Bronchogenic cyst

11. Descending aortic interface • Abnormalities in the descending aortic interface imply pathology within the posterior mediastinum Descending thoracic aortic aneuryam

12. Descriptive features of mediastinal masses

13. Descriptive features of mediastinal masses Thyroid adenoma

14. 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

15. 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 Division of the mediastinum

16. 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

18. Thymoma v.s. Bronchogenic cyst

19. 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

20. 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

21. 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

22. Thymoma

23. 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

24. 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

25. 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

26. Bronchogenic cyst

27. Other methods of diagnostic radiology

28. 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

29. 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

30. Thanks for your attention !!