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The Use of Computed Tomography to Evaluate Suspected Mediastinal Tumors
The Use of Computed Tomography to Evaluate Suspected Mediastinal Tumors James J. Livesay, M.D. , Jerrold H. Mink, M.D., Henry J. Fee, M.D. , Marshall E. Bein, M.D., W. Frederick Sample, M.D., and Donald G. Mulder, M.D.
ABSTRACT Thirty patients with suspected mediastinal tumors were evaluated by computed tomography (CT) at UCLA Medical Center. Twenty patients with myasthenia gravis were examined for possible thymomas, benign and malignant; and 10 patients were studied for other mediastinal masses (including teratoma, seminoma, mediastinal lipomatosis, carcinoma, lymphoma, and paravertebral abscess). The CT scan was found useful in several respects: (1) yielding information not available by conventional radiographic techniques; (2) defining the anatomical location and extent of mediastinal tumors; (3) detecting pulmonary metastasis and involvement of mediastinal nodes in cases of malignancy; and (4) establishing the diagnosis of benign mediastinal fatty masses. On the basis of our early experience, we believe CT is a valuable adjunct in the preoperative assessment of patients with suspected mediastinal tumors.
tumors. In this report we review our early experience with the use of CT to evaluate suspected mediastinal tumors. Materials and Methods
From June 1,1976, to September 2,1977, 30 patients with suspected mediastinal tumors were evaluated by CT at UCLA Medical Center. Twenty patients with myasthenia gravis were examined for possible thymoma. Ten additional patients were studied for other mediastinal lesions. The hospital records and all roentgenographic studies on each of these patients were carefully reviewed. Twenty-one patients underwent operation to establish the diagnosis. Six patients in this series were reported on previously [lll. All patients were initially evaluated by posteroanterior and lateral chest roentgenograms. Anterior oblique views were occasionally obtained and conventional mediastinal tomograms were frequently performed at 0.5-cm intervals in the anteroposterior, lateral, or left lateral decubitus positions, depending on the lesions studied. An EM1 CT 5000 body scanner was used for all CT studies. Scans were performed at 2-cm intervals from above the sternal notch to the diaphragm during suspended inspiration (20 seconds). Iodinated contrast infusion was occasionally used to distinguish vascular structures from suspected mediastinal tumors.
Mediastinal tumors may not be readily apparent on conventional roentgenograms of the chest. Subtle and often ill-defined contour abnormalities may be the only suggestion of mediastinal disease. Early experience with wholebody computed tomography (CT) proved it to be a valuable diagnostic procedure for studying the brain and abdomen [3, 18, 20, 211. Until recently, however, there were few published reports on the application of CT to the chest and mediastinum [2, 6, 9, 111. Accurate preoperative assessment by CT can yield valuable diagnostic information, influence the clinical management, and relate to the prog- Results nosis in patients with suspected mediastinal Thymoma in Myasthenia Gravis Twenty patients with myasthenia gravis were From the Departments of Surgery and Radiology, UCLA evaluated by CT scan for possible thymoma. Medical Center, Los Angeles, CA. Thirteen of them were operated on to establish Accepted for publication Nov 1, 1978. the diagnosis. Seven patients were not explored Address reprint requests to Dr. Mulder, Department of Surbecause either CT scan and tomography failed gery (Thoracic), UCLA Medical Center, Los Angeles, CA 90024. to confirm the presence of thymoma and the 305
0003-4975/79/040305-07$01.25 @ 1978 by James J. Livesay
306 The Annals of Thoracic Surgery Vol 27 No 4 April 1979
Fig I . CT scan shows a water density thymic cyst in the anterior mediastinum. Adjacent mediastinal structures are seen clearly. (TC = thymic cyst; Ao = aorta; SVC = superior vena cava; PA = pulmonary artery; LB = left bronchus.)
Fig 2 . CT scan of a malignant thymoma ( T )in a patient with myasthenia gravis. Note the extension of the tumor to the left pulmonary artery (LPA). (Ao = aorta; SVC = superior vena cava; C = carina.)
symptoms were minimal, or the patient refused mass. The surgical specimen consisted of an epithelioid thymoma with a single, densely caloperation (1patient). In 10 of the 14 positive CT scans, significant cified nodule at one pole. diagnostic information was obtained that was In 4 patients with malignant thymoma, CT not available by conventional roentgenographic scan demonstrated the extent of mediastinal inexamination. In 3 patients, plain chest roent- volvement and before operation twice idengenograms were normal, while lateral medias- tified pleural metastasis not otherwise detected. tinal tomograms revealed only an ill-defined In 1 patient, an invasive thymoma extended anterior mediastinal density. CT scan con- posteriorly to involve the pericardium, main firmed the presence of thymoma in each patient. pulmonary artery, and left pleura (Fig 2). These In 2 patients with obvious anterior medias- findings were suspected before operation on tinal tumors seen on plain chest roentgeno- the basis of the CT scan and were confirmed at gram, CT scan demonstrated a well-delineated operation. In a second patient, pleural metassmooth-walled mass of water density (Fig 1).In tasis to the chest wall and diaphragm were 1, the mass was separated from adjacent found at operation to correspond exactly to the mediastinal structures by a sharp, low-density, findings on CT scan. In 2 patients with obvious cleavage plane, suggesting a benign thymoma. superior vena cava syndrome, extensive At operation, a large thymic cyst was found in a mediastinal involvement was confirmed by CT hyperplastic gland. In the other patient, a large scan (Fig 3 ) . These patients were judged inthymic cyst was confirmed by transthoracic operable and were treated with high-dose, alternate-day prednisone. aspiration needle biopsy under CT guidance. In 1patient, a calcified retrosternal mass was identified on plain roentgenograms. However, O t h e r Mediastinal T u m o r s it could not be determined whether the mass Ten patients with other mediastinal tumors was in the mediastinum or the medial aspect of were evaluated by CT scan as well, and 8 one of the upper lobes. CT scan demonstrated underwent operation. Two patients had large the calcification in an anterior mediastinal mediastinal masses, obvious on plain chest
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Fig 3. CT scan of a malignant thymoma in the superior mediastinum demonstrates extensive tumor invasion of the right hemithorax with obstruction of the superior vena cava. (T = tumor; Tr = trachea.)
Fig 4 . CT scan of a malignant teratoma shows a large mediastinal tumor extending into the left hemithorax. Note the variable density in the central portion of the mass (arrows)found to be cystic degeneration of the tumor.
roentgenograms. In 1, CT revealed cystic degeneration of a large anterior mediastinal tumor with extension into the left hemithorax and adjacent pericardium, suggesting a malignant teratoma (Fig 4). The patient underwent a radi-
cal left pneumonectomy with en bloc resection of the anterior mediastinal tumor. Pathological examination confirmed the diagnosis of malignant teratoma. In the second of these 2 patients, CT scan revealed a large homogeneous mass extensively involving adjacent mediastinal structures. Exploratory thoracotomy revealed an unresectable seminoma, and the patient was treated with radiation therapy. In a patient with a normal plain chest roentgenogram, CT scan
308 The Annals of Thoracic Surgery Vol 27 No 4 April 1979
A
B
Fig 5 . Initial CT scan of a malignant lymphoma invading the heart. ( A ) Note the extensive tumor mass ( T )involving the aorta (Ao),pulmonary artery (PA),and the superior vena cava (SVC).( B ) Repeat CT scan following radiotherapy showing complete regression of the mass.
demonstrated an anterior mediastinal mass involving the heart (Fig 5). At operation a malignant lymphoma invading the pericardium, right atrium, and right ventricle was found. This patient was treated with radiation therapy and chemotherapy. In 2 patients a mediastinal tumor was suspected because of a widened mediastinal silhouette on chest roentgenograms. The finding on CT scan of a homogeneous, low-density zone surrounding the great vessels was diagnostic of benign mediastinal lipomatosis (Fig 6 ) . Thoracotomy was not performed. One patient with marked kyphosis was studied for a posterior mediastinal mass; tomography revealed erosion of the bodies of the fifth and sixth thoracic vertebrae (Fig 7A). CT scan demonstrated a large mass surrounding the thoracic spine with extensive destruction of vertebrae and adjacent ribs (Fig 78). At operation, a staphylococcal paravertebral abscess was found; thorough debridement, closed drainage, and anterior spinal fusion were performed. Four patients with metastatic disease involving mediastinal lymph nodes were studied. Recurrent disease in mediastinal lymph nodes was detected by a follow-up CT scan and con-
Fig 6 . CT scan of a suspicious mediastinal mass revealed a homogeneous low-density zone surrounding the great vessels and diagnostic for mediastinal lipomatosis. ( A A = aortic arch; VC = superior vena cava; F = f a t . )
firmed by conventional tomography in 1 patient who had undergone bilateral thoracotomy for metastatic embryonal cell carcinoma. In another patient with malignant lymphoma, CT scan was useful in demonstrating enlarged subcarinal nodes and in differentiating an abnormal cardiophrenic lymph node from the cardiophrenic fat pad (Fig 8). CT scan was found to be a sensitive indicator of peritracheal and subcarinal nodal involvement.
309
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A Fig 7. (A) Lateral tomograrn of the thoracic spine demonstrates a severe gibbus deformity from destruction of the fifth and sixth vertebral bodies. (B)CT scan reveals the extent of the paravertebral abscess (A) and shows destruction of vertebrae and adjacent rib (arrows).
B
A
B
Fig 8 . CT scan of a patient with malignant lymphoma shows abnormal mediastinal nodes. (A) Note the enlarged subcarinal node and (B)the abnormal epicardial node along the left cardiophrenic angle. (N = node; Ao = aorta; Br = bronchus.)
cent mediastinal structures and, therefore, may be difficult to diagnose on conventional roentgenographic examination. CT is a recent innovation in diagnostic radiology which allows precise images of anatomical areas previously inaccessible by conventional radiographic techniques. A number of reports have confirmed the value of CT scan of the brain [3] and abdomen [18, 20, 211, but until recently, few have dealt with its use in diseases of the chest and mediastinum [2, 6, 9, 111. Since UCLA Medical Center is a regional re-
Comment The discovery of a mediastinal tumor on chest roentgenogram is an important finding. Since one-third of these tumors are malignant, early diagnosis and treatment are mandatory [15]. Mediastinal tumors may blend in with adja-
310 The Annals of Thoracic Surgery Vol 27 No 4 April 1979
ferral center for patients with myasthenia gravis, we had the opportunity to study 20 patients for possible thymoma. In addition to plain chest roentgenograms and lateral tomograms of the anterior mediastinum, each patient was evaluated by CT scan for possible thymoma. Eight to 15% of patients with myasthenia gravis have a thymoma, either benign or malignant [lo, 231. Operative intervention is recommended when a mediastinal mass is found in a patient with myasthenia since 10 to 37% of thymomas in this syndrome are malignant [51 and thymectomy favorably alters the course of the disease in many patients [14]. Thymomas are located in the anterosuperior mediastinum, usually at the level of the aortic arch. There may be considerable difficulty detecting thymic lesions on routine chest roentgenograms. Ellis and Gregg [4]were unable to visualize thymic neoplasms by posteroanterior roentgenogram in 30% of their patients. The only clue to the presence of a tumor may be a subtle contour abnormality in the mediastinum. Lateral roentgenograms are more helpful but in 50% of patients they reveal only an ill-defined density [B]. Calcifications may facilitate the diagnosis but, in our experience, are rarely present. Mediastinal tomography in the lateral projection has been recommended to investigate suspicious findings on routine chest roentgenograms [4, 81. In the 20 patients with myasthenia gravis, the CT scan gave remarkably clear images of mediastinal structures. A thymic tumor could be identified in the anterior mediastinum as a mass that distorted the normally concave appearance of the retrosternal pleural envelope. A unique feature of the CT scan is that it allows precise measurement of tissue density. This enabled us to correctly distinguish a fluid-filled thymic cyst from adjacent mediastinal structures. Transthoracic aspiration needle biopsy under CT guidance confirmed the diagnosis. At times the thymoma was seen separated from other mediastinal structures by a less dense ”cleavage plane” of fat. Although a fibrous capsule and lack of invasion of surrounding fat are favorable histological indicators of a benign thymoma, the importance of the cleavage plane is not known [l].
Malignant thymomas spread by local invasion to involve adjacent mediastinal structures and metastasize to pleural surfaces. Radical excision of the tumor, if possible, may preclude future problems with superior vena cava obstruction and pleural effusion [131. Operation combined with high-dose, alternate-day prednisone and radiation therapy are the treatments of choice in malignant thymoma [5]. The CT scan was helpful in assessing the extent of mediastinal involvement in 3 patients and twice demonstrated encasement of the superior vena cava by tumor. Both patients were judged inoperable, and adjuvant therapy was instituted. Pleural and subpleural metastases may go undetected by plain roentgenogram since there is less inherent contrast at the peripheral portions of the lung. In 1 patient, CT scan revealed pleural metastasis that was not visualized on plain chest roentgenograms and thereby made the correct diagnosis of metastatic thymoma before operation. This result supports previous evidence that the CT scan may be very useful in detecting pleural metastasis [12, 193. The precise images of cross-sectional anatomy seen on CT scan accurately revealed the location and extent of mediastinal tumors. Two large mediastinal tumors were examined by CT scan. In 1, cystic degeneration was identified, as well as extensive involvement of adjacent structures. Although size and consistency (i.e., solid or cystic) are not considered to be reliable indicators of malignancy, the patient’s age (16 years) and the invasive appearance on CT scan led to the correct preoperative diagnosis of malignant teratoma. These tumors generally have a poor prognosis, although some recent evidence suggests adjuvant therapy may be worthwhile [71. Another large lobulated tumor, a seminoma, was thought to be highly invasive on CT scan and was found to be unresectable at operation. The unusual finding of a primary malignant lymphoma of the heart could be detected before operation only by CT scan. Radiation therapy has been recommended in such cases in the past 116, 221. In other cases of malignancy, CT scan was found to be a useful indicator of mediastinal nodal involvement. Metastatic disease to peritracheal
311 Livesay et al: Computed Tomography for Mediastinal Tumors
tomography of the mediastinum: normal and subcarinal nodes was detected by CT scan anatomy and indications for the use of CT. in 4 patients. Radiology 124:235, 1977 CT was also helpful in assessing the extent of 7. Grosfeld JL, Ballantine TVN, Lowe D, et al: Bea posterior mediastinal mass in a patient with a nign and malignant teratomas in children: analyparavertebral abscess. The anterior extent of the sis of 85 patients. Surgery 80:297, 1976 abscess seen on CT scan affected the operative 8. Harper RAK, Guyer PB: The radiological features of thymic tumors: a review of 65 cases. Clin approach. Laminagraphy revealed extensive Radiol 16:97, 1965 destruction of the vertebral bodies demon9. Jost RG: Computed tomography of the thorax. strated to a lesser degree by CT scan. This paRadiology 126:125, 1978 tient was treated by thoracotomy, debridement, 10. Keynes GL: The results of thymectomy in myasand spinal fusion. thenia gravis. Br Med J 2:611, 1949 In 2 patients, mediastinal tumors were sus- 11. Mink JH, Bein ME, Sukov R, et al: Computed tomography of the anterior mediastinum in papected on plain chest roentgenograms. CT scan tients with myasthenia gravis and suspected of the chest revealed mediastinal lipomatosis. thymoma. Am J Roentgenol 130:239, 1978 Both patients were reassured of the benign na- 12. Muhm JR, Brown LR, Crowe JK: Detection of ture of the condition and thoracotomy was not pulmonary nodules by computed tomography. necessary to establish the diagnosis. Because Am J Roentgenol 128:267, 1977 13. Mulder DG, Braitman H, Li W, et al: Surgical CT scan can determine relative tissue density, it management in myasthenia gravis. J Thorac Caris the only modality at present that can show diovasc Surg 63:105, 1972 intrathoracic tissue to be fat. Rohlfing and co- 14. Mulder DG, Herrmann C, Buckberg GD: Effect of workers [171 reported CT to be a reliable judge thymectomy in patients with myasthenia gravis: of fatty masses in the mediastinum. a 16 year experience. Am J Surg 128:202, 1974 On the basis of our early experience with CT, 15. Oldham HN Jr: Mediastinal tumors and cysts (collective review). Ann Thorac Surg 11:246,1971 we have found it to be a valuable adjunct to 16. Petersen CD, Robinson WA, Kumick JE: Inconventional roentgenograms in the evaluation volvement of the heart and pericardium in of suspected mediastinal tumors. CT can reveal malignant lymphomas. Am J Med Sci 272:161, additional diagnostic information which may 1976 influence the clinical management or relate to 17. Rohlfing BM, Korobkin M, Hall AD: Computed tomography of intrathoracic omental herniation the patient’s prognosis. The ultimate role of this and other mediastinal fatty masses. J Computer new modality will depend on its superiority to Assisted Tomog 1:181, 1977 other methods, its availability, and its cost- 18. Sagel S, Stanley RJ, Evens RG: Early clinical exeffectiveness. The present report documents the perience with motionless whole-body computed first of these. tomography. Radiology 119:321, 1976
References 1. Castleman 8, Norris EH: Pathology of the thymus in myasthenia gravis: a study of 35 cases. Medicine (Baltimore) 28:27, 1959 2. Crowe JK, Brown LR, Muhm JR: Computed to-
3. 4. 5. 6.
mography of the mediastinum. Computed Tomog 128:75, 1978 David DO, Pressman BD: Computerized tomography of the brain. Radiol Clin North Am 12:297, 1974 Ellis K, Gregg HG: Thymomas-roentgen considerations. Am J Roentgenol 91:105, 1964 Goldman AJ, Herrmann C, Keesey JC, et al: Myasthenia gravis and invasive thymoma: a 20 year experience. Neurology 25:1021, 1975 Goldwin RL, Heitzman R, Proto AV: Computed
19. Schaner EG, Chang AE, Doppman JL, et al: Comparison of computed and conventional whole lung tomography in detecting pulmonary nodules: a prospective radiologic-pathologic study. Am J Roentgenol 131:51, 1978 20. Sheedy PF, Stephens DH, Hattery RR, et al: Computed tomography of the body: initial clinical trial with the EM1 prototype. Am J Roentgenol 127:23, 1976 21. Stanley RJ, Sagel SS, Levitt RG: Computed tomography of the body: early trends in application and accuracy of the method. Am J Roentgenol 127:53, 1976 22. Sterchi M, Cordell AR: Seminoma of the anterior mediastinum. Ann Thorac Surg 19:371, 1975 23. Wilkins EW, Edmunds LH, Castleman 8 : Cases of thymoma at the Massachusetts General Hospital. J Thorac Cardiovasc Surg 52:322, 1966
ABSTRACT Thirty patients with suspected mediastinal tumors were evaluated by computed tomography (CT) at UCLA Medical Center. Twenty patients with myasthenia gravis were examined for possible thymomas, benign and malignant; and 10 patients were studied for other mediastinal masses (including teratoma, seminoma, mediastinal lipomatosis, carcinoma, lymphoma, and paravertebral abscess). The CT scan was found useful in several respects: (1) yielding information not available by conventional radiographic techniques; (2) defining the anatomical location and extent of mediastinal tumors; (3) detecting pulmonary metastasis and involvement of mediastinal nodes in cases of malignancy; and (4) establishing the diagnosis of benign mediastinal fatty masses. On the basis of our early experience, we believe CT is a valuable adjunct in the preoperative assessment of patients with suspected mediastinal tumors.
tumors. In this report we review our early experience with the use of CT to evaluate suspected mediastinal tumors. Materials and Methods
From June 1,1976, to September 2,1977, 30 patients with suspected mediastinal tumors were evaluated by CT at UCLA Medical Center. Twenty patients with myasthenia gravis were examined for possible thymoma. Ten additional patients were studied for other mediastinal lesions. The hospital records and all roentgenographic studies on each of these patients were carefully reviewed. Twenty-one patients underwent operation to establish the diagnosis. Six patients in this series were reported on previously [lll. All patients were initially evaluated by posteroanterior and lateral chest roentgenograms. Anterior oblique views were occasionally obtained and conventional mediastinal tomograms were frequently performed at 0.5-cm intervals in the anteroposterior, lateral, or left lateral decubitus positions, depending on the lesions studied. An EM1 CT 5000 body scanner was used for all CT studies. Scans were performed at 2-cm intervals from above the sternal notch to the diaphragm during suspended inspiration (20 seconds). Iodinated contrast infusion was occasionally used to distinguish vascular structures from suspected mediastinal tumors.
Mediastinal tumors may not be readily apparent on conventional roentgenograms of the chest. Subtle and often ill-defined contour abnormalities may be the only suggestion of mediastinal disease. Early experience with wholebody computed tomography (CT) proved it to be a valuable diagnostic procedure for studying the brain and abdomen [3, 18, 20, 211. Until recently, however, there were few published reports on the application of CT to the chest and mediastinum [2, 6, 9, 111. Accurate preoperative assessment by CT can yield valuable diagnostic information, influence the clinical management, and relate to the prog- Results nosis in patients with suspected mediastinal Thymoma in Myasthenia Gravis Twenty patients with myasthenia gravis were From the Departments of Surgery and Radiology, UCLA evaluated by CT scan for possible thymoma. Medical Center, Los Angeles, CA. Thirteen of them were operated on to establish Accepted for publication Nov 1, 1978. the diagnosis. Seven patients were not explored Address reprint requests to Dr. Mulder, Department of Surbecause either CT scan and tomography failed gery (Thoracic), UCLA Medical Center, Los Angeles, CA 90024. to confirm the presence of thymoma and the 305
0003-4975/79/040305-07$01.25 @ 1978 by James J. Livesay
306 The Annals of Thoracic Surgery Vol 27 No 4 April 1979
Fig I . CT scan shows a water density thymic cyst in the anterior mediastinum. Adjacent mediastinal structures are seen clearly. (TC = thymic cyst; Ao = aorta; SVC = superior vena cava; PA = pulmonary artery; LB = left bronchus.)
Fig 2 . CT scan of a malignant thymoma ( T )in a patient with myasthenia gravis. Note the extension of the tumor to the left pulmonary artery (LPA). (Ao = aorta; SVC = superior vena cava; C = carina.)
symptoms were minimal, or the patient refused mass. The surgical specimen consisted of an epithelioid thymoma with a single, densely caloperation (1patient). In 10 of the 14 positive CT scans, significant cified nodule at one pole. diagnostic information was obtained that was In 4 patients with malignant thymoma, CT not available by conventional roentgenographic scan demonstrated the extent of mediastinal inexamination. In 3 patients, plain chest roent- volvement and before operation twice idengenograms were normal, while lateral medias- tified pleural metastasis not otherwise detected. tinal tomograms revealed only an ill-defined In 1 patient, an invasive thymoma extended anterior mediastinal density. CT scan con- posteriorly to involve the pericardium, main firmed the presence of thymoma in each patient. pulmonary artery, and left pleura (Fig 2). These In 2 patients with obvious anterior medias- findings were suspected before operation on tinal tumors seen on plain chest roentgeno- the basis of the CT scan and were confirmed at gram, CT scan demonstrated a well-delineated operation. In a second patient, pleural metassmooth-walled mass of water density (Fig 1).In tasis to the chest wall and diaphragm were 1, the mass was separated from adjacent found at operation to correspond exactly to the mediastinal structures by a sharp, low-density, findings on CT scan. In 2 patients with obvious cleavage plane, suggesting a benign thymoma. superior vena cava syndrome, extensive At operation, a large thymic cyst was found in a mediastinal involvement was confirmed by CT hyperplastic gland. In the other patient, a large scan (Fig 3 ) . These patients were judged inthymic cyst was confirmed by transthoracic operable and were treated with high-dose, alternate-day prednisone. aspiration needle biopsy under CT guidance. In 1patient, a calcified retrosternal mass was identified on plain roentgenograms. However, O t h e r Mediastinal T u m o r s it could not be determined whether the mass Ten patients with other mediastinal tumors was in the mediastinum or the medial aspect of were evaluated by CT scan as well, and 8 one of the upper lobes. CT scan demonstrated underwent operation. Two patients had large the calcification in an anterior mediastinal mediastinal masses, obvious on plain chest
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Livesay et al: Computed Tomography for Mediastinal Tumors
Fig 3. CT scan of a malignant thymoma in the superior mediastinum demonstrates extensive tumor invasion of the right hemithorax with obstruction of the superior vena cava. (T = tumor; Tr = trachea.)
Fig 4 . CT scan of a malignant teratoma shows a large mediastinal tumor extending into the left hemithorax. Note the variable density in the central portion of the mass (arrows)found to be cystic degeneration of the tumor.
roentgenograms. In 1, CT revealed cystic degeneration of a large anterior mediastinal tumor with extension into the left hemithorax and adjacent pericardium, suggesting a malignant teratoma (Fig 4). The patient underwent a radi-
cal left pneumonectomy with en bloc resection of the anterior mediastinal tumor. Pathological examination confirmed the diagnosis of malignant teratoma. In the second of these 2 patients, CT scan revealed a large homogeneous mass extensively involving adjacent mediastinal structures. Exploratory thoracotomy revealed an unresectable seminoma, and the patient was treated with radiation therapy. In a patient with a normal plain chest roentgenogram, CT scan
308 The Annals of Thoracic Surgery Vol 27 No 4 April 1979
A
B
Fig 5 . Initial CT scan of a malignant lymphoma invading the heart. ( A ) Note the extensive tumor mass ( T )involving the aorta (Ao),pulmonary artery (PA),and the superior vena cava (SVC).( B ) Repeat CT scan following radiotherapy showing complete regression of the mass.
demonstrated an anterior mediastinal mass involving the heart (Fig 5). At operation a malignant lymphoma invading the pericardium, right atrium, and right ventricle was found. This patient was treated with radiation therapy and chemotherapy. In 2 patients a mediastinal tumor was suspected because of a widened mediastinal silhouette on chest roentgenograms. The finding on CT scan of a homogeneous, low-density zone surrounding the great vessels was diagnostic of benign mediastinal lipomatosis (Fig 6 ) . Thoracotomy was not performed. One patient with marked kyphosis was studied for a posterior mediastinal mass; tomography revealed erosion of the bodies of the fifth and sixth thoracic vertebrae (Fig 7A). CT scan demonstrated a large mass surrounding the thoracic spine with extensive destruction of vertebrae and adjacent ribs (Fig 78). At operation, a staphylococcal paravertebral abscess was found; thorough debridement, closed drainage, and anterior spinal fusion were performed. Four patients with metastatic disease involving mediastinal lymph nodes were studied. Recurrent disease in mediastinal lymph nodes was detected by a follow-up CT scan and con-
Fig 6 . CT scan of a suspicious mediastinal mass revealed a homogeneous low-density zone surrounding the great vessels and diagnostic for mediastinal lipomatosis. ( A A = aortic arch; VC = superior vena cava; F = f a t . )
firmed by conventional tomography in 1 patient who had undergone bilateral thoracotomy for metastatic embryonal cell carcinoma. In another patient with malignant lymphoma, CT scan was useful in demonstrating enlarged subcarinal nodes and in differentiating an abnormal cardiophrenic lymph node from the cardiophrenic fat pad (Fig 8). CT scan was found to be a sensitive indicator of peritracheal and subcarinal nodal involvement.
309
Livesay et al: Computed Tomography for Mediastinal Tumors
A Fig 7. (A) Lateral tomograrn of the thoracic spine demonstrates a severe gibbus deformity from destruction of the fifth and sixth vertebral bodies. (B)CT scan reveals the extent of the paravertebral abscess (A) and shows destruction of vertebrae and adjacent rib (arrows).
B
A
B
Fig 8 . CT scan of a patient with malignant lymphoma shows abnormal mediastinal nodes. (A) Note the enlarged subcarinal node and (B)the abnormal epicardial node along the left cardiophrenic angle. (N = node; Ao = aorta; Br = bronchus.)
cent mediastinal structures and, therefore, may be difficult to diagnose on conventional roentgenographic examination. CT is a recent innovation in diagnostic radiology which allows precise images of anatomical areas previously inaccessible by conventional radiographic techniques. A number of reports have confirmed the value of CT scan of the brain [3] and abdomen [18, 20, 211, but until recently, few have dealt with its use in diseases of the chest and mediastinum [2, 6, 9, 111. Since UCLA Medical Center is a regional re-
Comment The discovery of a mediastinal tumor on chest roentgenogram is an important finding. Since one-third of these tumors are malignant, early diagnosis and treatment are mandatory [15]. Mediastinal tumors may blend in with adja-
310 The Annals of Thoracic Surgery Vol 27 No 4 April 1979
ferral center for patients with myasthenia gravis, we had the opportunity to study 20 patients for possible thymoma. In addition to plain chest roentgenograms and lateral tomograms of the anterior mediastinum, each patient was evaluated by CT scan for possible thymoma. Eight to 15% of patients with myasthenia gravis have a thymoma, either benign or malignant [lo, 231. Operative intervention is recommended when a mediastinal mass is found in a patient with myasthenia since 10 to 37% of thymomas in this syndrome are malignant [51 and thymectomy favorably alters the course of the disease in many patients [14]. Thymomas are located in the anterosuperior mediastinum, usually at the level of the aortic arch. There may be considerable difficulty detecting thymic lesions on routine chest roentgenograms. Ellis and Gregg [4]were unable to visualize thymic neoplasms by posteroanterior roentgenogram in 30% of their patients. The only clue to the presence of a tumor may be a subtle contour abnormality in the mediastinum. Lateral roentgenograms are more helpful but in 50% of patients they reveal only an ill-defined density [B]. Calcifications may facilitate the diagnosis but, in our experience, are rarely present. Mediastinal tomography in the lateral projection has been recommended to investigate suspicious findings on routine chest roentgenograms [4, 81. In the 20 patients with myasthenia gravis, the CT scan gave remarkably clear images of mediastinal structures. A thymic tumor could be identified in the anterior mediastinum as a mass that distorted the normally concave appearance of the retrosternal pleural envelope. A unique feature of the CT scan is that it allows precise measurement of tissue density. This enabled us to correctly distinguish a fluid-filled thymic cyst from adjacent mediastinal structures. Transthoracic aspiration needle biopsy under CT guidance confirmed the diagnosis. At times the thymoma was seen separated from other mediastinal structures by a less dense ”cleavage plane” of fat. Although a fibrous capsule and lack of invasion of surrounding fat are favorable histological indicators of a benign thymoma, the importance of the cleavage plane is not known [l].
Malignant thymomas spread by local invasion to involve adjacent mediastinal structures and metastasize to pleural surfaces. Radical excision of the tumor, if possible, may preclude future problems with superior vena cava obstruction and pleural effusion [131. Operation combined with high-dose, alternate-day prednisone and radiation therapy are the treatments of choice in malignant thymoma [5]. The CT scan was helpful in assessing the extent of mediastinal involvement in 3 patients and twice demonstrated encasement of the superior vena cava by tumor. Both patients were judged inoperable, and adjuvant therapy was instituted. Pleural and subpleural metastases may go undetected by plain roentgenogram since there is less inherent contrast at the peripheral portions of the lung. In 1 patient, CT scan revealed pleural metastasis that was not visualized on plain chest roentgenograms and thereby made the correct diagnosis of metastatic thymoma before operation. This result supports previous evidence that the CT scan may be very useful in detecting pleural metastasis [12, 193. The precise images of cross-sectional anatomy seen on CT scan accurately revealed the location and extent of mediastinal tumors. Two large mediastinal tumors were examined by CT scan. In 1, cystic degeneration was identified, as well as extensive involvement of adjacent structures. Although size and consistency (i.e., solid or cystic) are not considered to be reliable indicators of malignancy, the patient’s age (16 years) and the invasive appearance on CT scan led to the correct preoperative diagnosis of malignant teratoma. These tumors generally have a poor prognosis, although some recent evidence suggests adjuvant therapy may be worthwhile [71. Another large lobulated tumor, a seminoma, was thought to be highly invasive on CT scan and was found to be unresectable at operation. The unusual finding of a primary malignant lymphoma of the heart could be detected before operation only by CT scan. Radiation therapy has been recommended in such cases in the past 116, 221. In other cases of malignancy, CT scan was found to be a useful indicator of mediastinal nodal involvement. Metastatic disease to peritracheal
311 Livesay et al: Computed Tomography for Mediastinal Tumors
tomography of the mediastinum: normal and subcarinal nodes was detected by CT scan anatomy and indications for the use of CT. in 4 patients. Radiology 124:235, 1977 CT was also helpful in assessing the extent of 7. Grosfeld JL, Ballantine TVN, Lowe D, et al: Bea posterior mediastinal mass in a patient with a nign and malignant teratomas in children: analyparavertebral abscess. The anterior extent of the sis of 85 patients. Surgery 80:297, 1976 abscess seen on CT scan affected the operative 8. Harper RAK, Guyer PB: The radiological features of thymic tumors: a review of 65 cases. Clin approach. Laminagraphy revealed extensive Radiol 16:97, 1965 destruction of the vertebral bodies demon9. Jost RG: Computed tomography of the thorax. strated to a lesser degree by CT scan. This paRadiology 126:125, 1978 tient was treated by thoracotomy, debridement, 10. Keynes GL: The results of thymectomy in myasand spinal fusion. thenia gravis. Br Med J 2:611, 1949 In 2 patients, mediastinal tumors were sus- 11. Mink JH, Bein ME, Sukov R, et al: Computed tomography of the anterior mediastinum in papected on plain chest roentgenograms. CT scan tients with myasthenia gravis and suspected of the chest revealed mediastinal lipomatosis. thymoma. Am J Roentgenol 130:239, 1978 Both patients were reassured of the benign na- 12. Muhm JR, Brown LR, Crowe JK: Detection of ture of the condition and thoracotomy was not pulmonary nodules by computed tomography. necessary to establish the diagnosis. Because Am J Roentgenol 128:267, 1977 13. Mulder DG, Braitman H, Li W, et al: Surgical CT scan can determine relative tissue density, it management in myasthenia gravis. J Thorac Caris the only modality at present that can show diovasc Surg 63:105, 1972 intrathoracic tissue to be fat. Rohlfing and co- 14. Mulder DG, Herrmann C, Buckberg GD: Effect of workers [171 reported CT to be a reliable judge thymectomy in patients with myasthenia gravis: of fatty masses in the mediastinum. a 16 year experience. Am J Surg 128:202, 1974 On the basis of our early experience with CT, 15. Oldham HN Jr: Mediastinal tumors and cysts (collective review). Ann Thorac Surg 11:246,1971 we have found it to be a valuable adjunct to 16. Petersen CD, Robinson WA, Kumick JE: Inconventional roentgenograms in the evaluation volvement of the heart and pericardium in of suspected mediastinal tumors. CT can reveal malignant lymphomas. Am J Med Sci 272:161, additional diagnostic information which may 1976 influence the clinical management or relate to 17. Rohlfing BM, Korobkin M, Hall AD: Computed tomography of intrathoracic omental herniation the patient’s prognosis. The ultimate role of this and other mediastinal fatty masses. J Computer new modality will depend on its superiority to Assisted Tomog 1:181, 1977 other methods, its availability, and its cost- 18. Sagel S, Stanley RJ, Evens RG: Early clinical exeffectiveness. The present report documents the perience with motionless whole-body computed first of these. tomography. Radiology 119:321, 1976
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19. Schaner EG, Chang AE, Doppman JL, et al: Comparison of computed and conventional whole lung tomography in detecting pulmonary nodules: a prospective radiologic-pathologic study. Am J Roentgenol 131:51, 1978 20. Sheedy PF, Stephens DH, Hattery RR, et al: Computed tomography of the body: initial clinical trial with the EM1 prototype. Am J Roentgenol 127:23, 1976 21. Stanley RJ, Sagel SS, Levitt RG: Computed tomography of the body: early trends in application and accuracy of the method. Am J Roentgenol 127:53, 1976 22. Sterchi M, Cordell AR: Seminoma of the anterior mediastinum. Ann Thorac Surg 19:371, 1975 23. Wilkins EW, Edmunds LH, Castleman 8 : Cases of thymoma at the Massachusetts General Hospital. J Thorac Cardiovasc Surg 52:322, 1966