Mediastinal assessment: More than the 4 "T"

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1 Mediastinal assessment: More than the 4 "T" Poster No.: C-1434 Congress: ECR 2011 Type: Educational Exhibit Authors: S. Juanpere, N. Cañete, G. Sanchez, S. Martinez, M. Turell, P. Ortuño Muro, A. Villar Cánovas, S. Pedraza; Girona/ES Keywords: Mediastinum, Thorax, CT, MR DOI: /ecr2011/C-1434 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 59

2 Learning objectives To have an overview of the imaging features of masses, tumors and tumor-like lesions of the anterior, middle and posterior mediastinum. To recognize the specific imaging appearances of some of these lesions by Chest Radiography (CR), Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). Page 2 of 59

3 Background The most frequent lesions encountered in the mediastinum are thymoma, neurogenic tumors, and benign cysts, altogether representing 60% of patients with mediastinal masses. Neurogenic tumors, germ cell neoplasms and foregut cysts represent 80% of childhood lesions. Primary thymic neoplasms, thyroid masses and lymphomas are the most frequent in adults. Most patients with mediastinal masses are usually asymptomatic. Eighty-three percent of incidentally discovered lesions are benign and 57% of those seen in symptomatic patients are malignant. Clinical symptoms can include dyspnea, dysphagia, cough from airway compression, superior vena cava syndrome, hoarseness from laryngeal nerve involvement, or symptoms resulting from spinal cord compression. Myasthenia gravis or Cushing's syndrome can also reveal mediastinal masses. Page 3 of 59

4 Imaging findings OR Procedure details Imaging Modalities CHEST RADIOGRAPHS (CR): Posteroanterior and lateral chest radiographs are the first imaging modalities used when a mediastinal mass is suspected. Deformation of mediastinal contours and lines or displacement of normal structures must be present to identify a mass. Tissular characterization is limited being only able to identify calcifications (fatty component can be suspected as a zone of relative radiolucency) (FIG 1). COMPUTED TOMOGRAPHY (CT): CT is the most important tool in the evaluation of a mediastinal mass. It is the next step following CR and in many times is sufficient in the management of the patient. Characterization on CT is based on specific attenuation of air, fat, water or calcium. Vascular abnormalities and the degree of vascularization of soft tissue masses can be demonstrated by contrast-enhanced study. Multiplanar reconstructions are a valuable adjunct to localize the lesion in the mediastinum (FIG 2A). MAGNETIC RESONANCE IMAGING (MRI): The excellent soft tissue contrast with spontaneous tissue-vessel contrast is an advantage in imaging the mediastinum by MRI. This modality is used when iodine constrast cannot be used, or after doubtful CT study. Assessment of preoperative relationships with the pericardium, heart cavities, spinal cord and vascular involvement is a common indication (FIG 3). ULTRASONOGRAPHY (US): Transthoracic US is not currently used in mediastinal mass evaluation. The major limitation is an inadequate window, but useful information can be obtained especially in children. TRANSTHORACIC NEEDLE BIOPSIES: Percutaneous fine-needle aspiration and core biopsies with large bore needles guided by CT scanning have been advocated for the diagnostic examination of mediastinal lesions. Indications the role of CT-guided biopsies depends on the importance paced on them by radiologists, pathologists, and surgeons (FIG 2B). Differential Diagnosis of Mediastinal Masses When a central mass is discovered on a CR, the first step is to be sure that this mass arises within the mediastinum. Masses that lie deep to mediastinal vessels are clearly mediastinal in origin as well as a normal remaining pleura. Page 4 of 59

5 The second step is to recognize abnormal radiographic findings related to anatomical variants such as aortic-arch abnormalities, or masses arising from the digestive tract (FIG 4) or from spine (FIG 5). Vascular anomalies represent approximately 10% of mediastinal masses and must be correctly recognized for its dramatic event (FIG 6). Mediastinal lymph nodes certainly represent the most common cause of mediastinal masses (FIG 7, 8 and 9). Certain Mediastinal Masses Radiological compartmentalization of mediastinum helps in focusing the differential diagnosis of masses on the basis of their site. Anatomists, Felson, or Heitzman have used different references in order to divide the mediastinum. However, in any method used, the divisions are theoretic rather than physical. Therefore, disease can spread from one compartment to another, and some diseases do not occur exclusively in any one compartment. It is often more instructive to determine precisely where an abnormality lies as well as tissue components shown by CT or MRI, size, and shape to elaborate an accurate diagnosis of a mediastinal mass. FATTY MASSES Fat is specifically recognized by its low CT attenuation, which vary from -70 to -130 HU. On MRI well-differentiated fat has an high signal intensity on T1-weighted sequence. In the majority of cases, discovery of the fatty nature of a mass indicates benignancy. Herniation of abdominal fat is not a true primary fatty lesion but is much more common than this (FIG 10). MEDIASTINAL DIFFUSE LIPOMATOSIS It is an overabundant amount of histologically normal fat resulting in smooth mediastinal widening on chest radiographs. Upper mediastinum, the cardiophrenic angles, and paraspinal areas are the usual locations. There is an absence of compression of surrounding structures. LIPOMAS AND LIPOSARCOMAS They represent only 1% of all primary mediastinal tumors. They do not produce compressive symptoms unless they are large enough. Liposarcomas show unhomogeneity of the fat and contain large areas of soft tissue density. They are often locally invasive at the time of diagnosis. TYMOLIPOMAS Page 5 of 59

6 Among tumors predominantly composed of fat, thymolipomas are the most common. These tumors develop in the thymic space. Especially when they are large, they may extend downwards on the diaphragm(fig 11). TERATOMAS Although most teratomas are cystic, some of them may contain a small amount of fatty tissue (FIG 36). Other uncommon lesions that may contain some fat include hemangiomas, angiolipomas, lipoblastomas in children, and extramedullary hematopoiesis. Fatty tissue component may be part of a complex mesenchymal sarcoma. CYSTIC MASSES Primary cysts represent 15-20% of all primary mediastinal masses. The majority of mediastinal cysts are developmental in origin. Typical cysts appear on CR as smooth, sharply marginated mediastinal lesions. On CT they have a similar attenuation to that of water and do not enhance (FIG 12). Their margins are well defined and their wall is barely perceptible. Any cyst may have a higher attenuation than that of water due to its calcic, proteinaceous, mucus, or hemorrhagic content. On MRI typical cysts have an high signal intensity on T2-weighted images. True cystic lesions should be differentiated from the cystic degenerative changes observed in many solid tissular tumors (goiters, thymomas, cystic teratomas, nerve root tumors, seminomas, and enlarged nodes), abscesses (FIG 13), and hematomas. Hodgkin's disease and other lymphomas can also be associated with cystic changes before or after treatment (FIG 33). BRONCHOGENIC CYSTS Bronchogenic cysts have a fibrous capsule, often contain cartilage, are lined by respiratory epithelium, and contain mucoid material. They are stable in size except when complicated by infection or hemorrhage. They do not usually communicate with the bronchial tree. Although most of them are located along the paratracheal wall, or in the posterior medastinum, sometimes they can be found in rare localizations (FIG 14). Curvilinear calcification of the wall is possible. DUPLICATION CYSTS Duplication cysts are indistinguishable from bronchogenic cysts, except for their location usually close to the esophagus, sometimes within its wall (FIG 15). Page 6 of 59

7 NEUROENTERIC CYSTS These masses are rare lesions which may be connected to the meninges through a midline defect in one or more vertebral bodies. Their communication with the subarachnoid spaces may be demonstrated by MRI. PERICARDIAL CYSTS Pericardial cysts are the result of anomalous outpouchings of the parietal pericardium. Most pericardial cysts are unilocular and commonly located in the right cardiophgrenic angle, although they may occur anywhere in relation to the pericardium (posterior cardiophrenic angle, superior retro-aortic pericardial recess) (FIG 16). On imaging studies they are seen as smooth, well-defined, oval or round masses in contact with the heart, without a perceptible wall (FIG 17 and 18). THYMIC CYSTS Two pathogenetically distinct forms of thymic cysts are described. A congenital one, which tends to be unilocular, derives from remmants of the thymopharyngeal duct. Apart from their characteristic water density, calcification has been reported. Thymic cysts can also be acquired lesions which tend to have multilocular aspect (FIG 19 and 20). Their histogenesis and natural history are controversial and poor-known. LYMPHANGIOMAS Lymphangiomas are tumor-like congential malformation of the lymphatic system, consisting of lymph channel or cystic lymph spaces lined by endothelium. Their vary in size and histology, some taking the form of unilocular or multilocular cysts. They may be difficult to resect and may recur due to their invasive nature. Fewer than 10% occur in the posterior mediastinum. Cysts of the thoracic duct and intrathoracic meningoceles are rare cysts lesions of the posterior mediastinum. SOLID TISSULAR MASSES Most mediastinal masses in adult population are solid. The CT technique is often sufficient in distinguishing invasive unresectable tumors from well-defined resectable lesions. MEDIASTINAL THYROID GOITERS Page 7 of 59

8 They represent a group of common mediastinal tumors with high attenuation on unenhanced CT (this finding is variable and relates to the iodine content of the goiter). An intrathoracic thyroid mass is usually a benign multinodular colloid goiter or an adenoma and seldomly a carcinoma. Malignant thoracic goiters are not more frequent than their neck counter-part. Ocasionally, symptoms of airway or esophageal compression are present. In most cases thyroid masses represent direct contiguous growth of a goiter into the mediastinum (FIG 21). An intrathoracic thyroid mass developing form heterotopic thyroid tissue without any connection to the thyroid in the neck is extremely rare (FIG 22). In 80% of cases the thyroid extends into the prevascular spaces. Typical features of mediastinal goiters are unhomogeneous density with cystic and high-density areas, calcifications of various shape, and marked and prolonged contrast enhancement. On MRI multinodular goiters have been shown to be relatively hypointense as compared with normal tissue on T1-weighted images. T2-weighted images show a typically heterogeneous appearance (FIG 23). Distinguishing between benign and malignant goiters at CT is not possible unless the tumor clearly invades beyond the thyroid gland (FIG 24). THYMIC MASSES The size of a normal thymus varies strongly with age. A normal thymus, in contradiction to a thymic mass, conforms to the shape of the adjacent great vessels on CT and MRI. Normal thymic tissue shows an homogeneous signal, whereas thymic masses often show unhomogeneous signal intensity. Thymomas Thymomas are tumors composed of an admixture of thymic epithelial cells and reactive lymphocytes. The predominantly epithelial variety carries the poorer prognosis. Thymomas are seen with equal frequency in men and women at a mean age of 50 years. Most patients have no symptoms, but thymomas are associated with a large variety of autoimmune diseases (myasthenia gravis, p.e.). Cystic changes are common and calcifications at the periphery of the lesion or throughout its substance, hemorrhage, or necrosis can also be seen. The presence or absence of spread beyond the capsule, determines whether a tumor is labeled benign or malignant. Fifteen-fourty percent of thymomas turn out to be invasive. Non-invasive thymomas appear as round or oval well-circumscribed masses growing asymmetrically to one side of the anterior mediastinum. The CT density is similar to that of a normal young thymus. The tumor can occur in the prevascular space but also around the base of the heart and anywhere between the lower pole of the thyroid gland and the anterior surface of the pericardium. Invasive thymoma appears on CT as an irregular ill-defined mass. They grow along pleural surfaces (FIG 25 and 26) and can reach the posterior mediastinum and extend Page 8 of 59

9 downwards along the aorta to involve the crus of the diaphragm and the retroperitoneum. Invasion of the thoracic wall, mediastinal vessels, trachea, pericardium, and lung parenchyma is frequent. CT is the most precise method for detecting local and regional spread (FIG 27). However, direct contact and absence of cleavage planes are not strictly reliable criteria to predict invasion. Vascular and cardiac extension of invasive thymoma is well identified by MRI (FIG 28). Thymic carcinoma This entity behaves more aggressively than invasive thymomas and CT features cannot help to distinguish between them. A local invasion along the pleura or mediastinum, as well as necrosis and calcifications, are frequent. Thymic carcinoid The CT features are indistinguishable from thymomas. They may secrete adrenocorticotropic hormone (ACTH) and present with an ectopic ACTH Cushing's syndrome. Thymic hyperplasia Thymic hyperplasia is a term used by pathologists to describe numerous active lymphoid germinal centers in the medulla. The thymic gland grows back to a larger-than-normal size after rapid atrophy in response to stress or therapy with antineoplasic or steroids. It has been reported after treatment of lymphomas, Cushing's syndrome, and recovery after a wide variety of other stresses. The role of CT and MRI is limited in detecting this abnormality because 50% of thymic hyperplasia appear entirely normal on CT. Typically, the appearance is a normally shaped enlarged gland which conforms to the shape of adjacent structures with a similar density to that of the normal gland (FIG 29). Distinguishing between hyperplasia from lymphoma in children and young adults may be very difficult. LYMPHOPROLIFERATIVE DISORDERS Mediastinal and hilar lymphadenopathies can be due to lymphoma and many other diseases. Lymphoma constitutes one of the most common mediastinal neoplasms and may affect any mediastinal compartment, although usually occurs in the anterior mediastinum as a part of a more widespread disease. Primary mediastinal lymphoma is a rare entity comprising only 10% of lymphomas in the mediastinum. Hodgkin and nonhodgkin lymphoma may have overlapping features. Hodgkin lymphoma Page 9 of 59

10 Hodgkin lymphoma is the most common mediastinal lymphoma representing approximately 50 to 70% of cases. Bimodal distribution of incidente peaking in young adulthood and again after age of 50 years. Four types are described: nodular sclerosing (more than 2/3 of cases) (FIG 30 and 31), mixed cellularity, lymphocyte-rich, and lymohocyte deplected. Most patients experience constitutional symptoms (B symptoms) including fever, night sweats and weight loss. Patients with mediastinal involvement may have also cough, dispnea, chest pain, pleural effussions and superior vena cava syndrome. Non-Hodgkin lymphoma Although there are many classes and grades, lymphoblastic lymphoma (highly aggressive) and large B-cell lymphoma are the most common subtypes. Both Hodgkin and non-hodgkin lymphomas can cause bulky nodal mediastinal disease. CT shows multiple rounded soft-tissue masses (lymph nodes) as a dominant bulky soft tissue mass (nodal coalescence). Masses typically exhibit homogeneous soft-tissue attenuation (FIG 32), but large tumors may demonstrate heterogeneity with complex low attenuation and fluid-like areas representing necrosis, hemorrhage and cyst formation (FIG 33). At MR study a relatively homogeneous mass or masses with low signal intensity on T1-weighted images (FIG 34) and mixed or high signal on T2-weighted images are seen. GERM CELL TUMORS Germ cell tumors arise from tumoral transformation of germinal elements. Sixty percent are benign teratomas that occur with equal frequency in men and women. Benign teratoma They usually consist of ectodermal elements such as skin, sebaceous material, hair, and calcification. Half the cases are asymptomatic. Most occur in the anterior mediastinum, but a few are found in the posterior mediastinum. They grow slowly and may be uni- or multiloculated (FIG 35). Benign teratomas typically contain a mixture of CT fatty, tissular, and water densities (FIG 36). Calcification in the wall or small spherical or irregular calcifications within the mass, sometimes suggesting dental material, may be seen. Malignant germ cell tumors Malignant varieties have a strong male predominance and include teratocarcinomas, embryonic carcinomas, seminomas (FIG 37), endodermal sinus tumor, choriocarcinomas, and mixtures of these cell types. These tumors grow rapidly and Page 10 of 59

11 metastases may be seen in the lung, pleura, or bone. They secrete beta human chorionic gonadotropin, alpha-fetoprotein, and lacticodehydrogenase. Malignant germ cell tumors have CT and MR features similar to other primary malignant tumors arising within the anterior mediastinum. The role of imaging modalities is to define disease extent and to monitor response to therapy together with serum tumor markers. NEUROGENIC TUMORS Neural tumors can be divided into nerve sheath tumors, ganglion cell tumors, and paraganglionic cell tumors. Nerve sheath tumors The nerve sheath tumors comprise schwannomas, neurofibromas and their malignant counterpart. All of them are common in neurofibromatosis. Schwannoma (FIG 38) is an eccentric and encapsulated tumor whereas neurofibroma is an unencapsulated mass. Most nerve sheath tumors are benign and asymptomatic, and are rare in people under 20 years. Ganglion cell tumors These group of tumors form a spectrum: neuroblastomas (malignant form) (FIG 39) and ganglioneuromas (benign form). They are essentially childhood tumors. These neurogenic tumors show the following radiological appearances: CR shows a sharply circumscribed round or oval mass located in the paravertebral gutter when the tumor arises from the nerve sheath. When arising from ganglia cells, they are more anteriorly located. Rib erosion with a sclerotic border is suggestive of a benign lesion. Spreading to multiple ribs with erosion or destruction is in favor of malignancy. Calcifcation may be seen in all types of neural tumors. On CT neurogenic tumors have a low-attenuation value attributed to lipid content and cystic degeneration. At MRI neurofibromas may show a so-called target pattern with a lower signal intensity in the central portion compared with the peripheral zone on T2-weighted images. Schwannomas may show inhomogeneity on T2-weighted images and on T1-weighted images after gadolinium injection. MRI can demonstrate spinal involvement. Paraganglionic cell tumors Paragangliomas are tumors of the paraganglionic cells. These masses are usually extremely vascular and enhance brightly at enhanced CT (FIG 40). At MRI they may show high signal intensity on T2-weighted images. Page 11 of 59

12 OTHER UNCOMMON MEDIASTINAL MASSES PARATHYROID MASSES Most parathyroid masses are adenomas or hyperplastic glands. They may occur in or near the thymus and they are often less than 2 cm. They show a marked contrast enhancement. Technetium-99 Sestamibi SPECT scans have been shown to be more effective in their detection than MRI and CT. CASTELMAN DISEASE Castelman disease (or giant lymph node hyperplasia, angiofollicular lymph node hyperplasia) is a variety of lymph node hyperplasia. It occurs at any age but frequently in young adults. AIDS and Kaposi sarcomas can be associated and patients may develop lymphomas. Well-defined large masses sometimes calcified in the mediastinum or proximal hilum are the radiological features. HEMANGIOMAS Blood vessel tumors in the mediastinum are rare. They tend to be well-circumscribed lesions without a true capsule. They typically occur in young patients and may be associated with Rendu-Osler syndrome. Phleboliths are seen rarely. On enhanced CT ther are heterogeneous masses of four distinct patterns of enhancement, in decreasing order of frequency: central, mixed central and peripheral, or peripheral. HEMATOMAS (FIG 41) Ninety percent of hematomas have areas of high attenuation during the first 72 h. At this stage the MR signal intensity is low on T1 and T2-weighted sequences. When the hematoma ages, its attenuation decreases at CT in a centripetal fashion creating a lowattenuation peripheral halo. At MRI the signal intensity on T1-weighted images increases. OTHERS Desmoid tumors are locally invasive tumors that are very rarely found in the mediastinum. Sarcomas other than vascular or neural origin, including fibrosarcomas, osteosarcomas, and chondrosarcomas (FIG 42), are also very uncommon. Idiopathic fibrosing mediastinitis (FIG 43) and extramedullary hematopoiesis in posterior mediastinum are other entities to take into account Page 12 of 59

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56 Conclusion Many mediastinal masses are discovered incidentally on chest radiographs. The most common primary mediastinal masses in adults are primary thymic neoplasms, mediastinal goiter and lymphoma. Radiologic evaluation of these patients begins with the chest radiograph and is followed by cross-sectional imaging with CT or MRI. Attenuation values at CT and signal intensity at MRI give much more detailed information than chest film concerning the tissular composition of the mass. The radiological diagnosis can be suggested based on the major component of the mass, the degree and type of vascularity of the lesion due to contrast enhancement on CT or MRI, and of course, its localization. All these factors with a well-known clinical history will allow a certain diagnosis in many cases. Page 56 of 59

57 Personal Information Sergi Juanpere Department of Diagnostic Radiology from Dr. Josep Trueta University Hospital, Girona, Spain. Av/ Francia s/n. Girona, España. Noemí Cañete Department of Diagnostic Radiology from Dr. Josep Trueta University Hospital, Girona, Spain Gloria Sanchez Department of Diagnostic Radiology from Dr. Josep Trueta University Hospital, Girona, Spain Sandra Martinez Department of Thoracic Surgery from Dr. Josep Trueta University Hospital, Girona, Spain Mariana Turell Department of Anatomical Pathology from Dr. Josep Trueta University Hospital, Girona, Spain Pedro Ortuño Department of Diagnostic Radiology from Dr. Josep Trueta University Hospital, Girona, Spain Page 57 of 59

58 References Noriyuki Tomiyama (2009) Anterior mediastinal tumors: Diagnostic accuracy of CT and MRI. European Journal of Radiology 69: Camilla R. Whitten (2007) A Diagnostic Approach to Mediastinal Abnormalities. RadioGraphics 27: Victor Pineda (2007) Lesions of the Cardiophrenic Space: Findings at Cross-sectional Imaging. RadioGraphics 27:19-32 Leslie E. Quint (2007). Imaging of anterior mediastinal masses. Cancer imaging. S56-S62 Junko Sadohara (2006) Thymic epithelial tumors: Comparison of CT and MR imaging findings of low-risk thymomas, high-risk thymomas, and thymic carcinomas. European Journal of Radiology 60:70-79 Mizuki Nishino et al. (2006) The Thymus: A Comprehensive Review. RadioGraphics 2006; 26: Sanjay Gupta (2005) Imaging-guided Percutaneous Biopsy of Mediastinal Lesions: Different Approaches and Anatomic Considerations. RadioGraphics 25: Duwe BV, Sterman DH, Musani AI. (2005) Tumors of the Mediastinum. Chest 128: Takeda S, Miyoshi S, Minami M et al. (2003) Clinical spectrum of medistinal cysts. Chest 124, Jeung MY, Gasser B, Gangi A et al. (2002) Imaging of cystic masses of the mediastinum. Radiographics 22; S79-S93 Scott C. Gaerte (2002) Fat-containing Lesions of the Chest. RadioGraphics 22:S61-S78 Buckley JA et al (1999) Intrathoracic mediastinal thyroid goiter :Imaging manifestations. AJR Am J Roentgenol173 (2):471-5 Page 58 of 59

59 F.Laurent (1998) Mediastinal masses: diagnostic approach. Eur Radiol 8: David M. Hansell, David A. Lynch, et al. HansellHansell & Armstrong, Tórax Diagnóstico Radiológico. MARBÁN. 4º Ed Page 59 of 59