The anterior mediastinum: diseases

Mediastinal tumours are frequently asymptomatic and first noted on routine chest radiograph. In most cases, evaluation should proceed to spiral computed tomography (sCT) of the chest with iodinated contrast material. The specific location and appearance of tumours on sCT is instrumental in planning further diagnostic and treatment strategies. Primary tumours in the anterior mediastinum account for half of all mediastinal masses. They comprise various benign and malignant neoplasms, but a wide variety of nonneoplastic lesions (developmental, inflammatory) can present as a localised mass in this compartment. The most common primary anterior mediastinal tumours are thymoma, teratoma and lymphoma; all other lesions are rare. Nonneoplastic conditions include thymic cysts, lymphangioma and intrathoracic goitre. Understanding the pathology, clinical presentation, imaging and diagnosis of the major tumour types is instrumental in the safe and efficient work-up of a mediastinal mass. Patients with primary mediastinal masses and cysts will usually undergo surgical resection; radiological and clinical features should prompt limited biopsy specimens followed by oncologic consultation, and chemotherapy or radiotherapy when appropriate. The objective of this review was to examine the role of diagnostic imaging in the management of masses of the anterior mediastinum.     

Narrow superior mediastinum and pseudomasses: CT features

The authors report three cases of abnormal chest radiography mimicking mediastinal masses. These radiographic findings were unrelated to any pathology, were discovered in asymptomatic patients, and must be considered consequences of unusually narrow thoracic inlets. Mean and standard deviations of the anteroposterior diameter of the superior mediastinum are given. Computed tomography of the chest yielded valuable diagnostic information and made it possible to exclude mediastinal masses.     

纵隔囊性淋巴管瘤的X线及CT诊断探讨

目的　探讨纵隔囊性淋巴管瘤 (CLM)X线和CT诊断。方法　回顾分析 10例CLM的胸部平片及其中 8例CT表现。结果　根据肿块发生部位 ,颈纵隔型 3例 ,纵隔型 7例。位于前纵隔 7例 ,后纵隔 2例 ,累及纵隔多区域及胸腔 1例。 8例位于中上纵隔或胸廓入口 ,胸片多数表现边缘光整的纵隔肿块 ,无纵隔移位 ;CT显示肿块为囊性 ,边界清晰 ,无周围侵犯 ,颈纵隔型CLG的纵隔肿块与颈部肿块贯通。结论　CLM多发生于前纵隔及中上纵隔 ,颈纵隔型CLG根据胸部影像表现及体征可以确诊 ,纵隔型CLG诊断需与纵隔其他囊性占位鉴别。     

Diagnostic imaging of mediastinal masses in children.

Mediastinal masses are the most common thoracic masses in children. The encyclopedic list of diagnostic considerations can be distilled into a concise and practical differential diagnosis based on the location of the mass and the established prevalence of various tumors and pseudotumors in the mediastinal compartments. Malignant lymphoma, benign thymic enlargement, teratomas, foregut cysts, and neurogenic tumors make up 80% of mediastinal masses in children. Continuing advances in imaging technology have altered traditional approaches to the evaluation and diagnosis of mediastinal masses in children. Plain chest radiography remains the basic imaging examination to define location and morphology. Cross-sectional imaging subsequently clarifies the morphology and extent of the mass. In general, CT is the primary cross-sectional imaging procedure in the evaluation of most mediastinal masses in children. Exceptions to this rule include MR in children with posterior mediastinal masses or suspected vascular lesions: in such cases, MR imaging is the preferred initial postradiographic examination. Sonographic examination may be diagnostic in foregut cysts and some other mediastinal masses. Gallium-67 scintigraphy has an emerging role in management of malignant lymphoma.     

US in the diagnosis of pediatric chest diseases.

Most pediatric chest diseases are adequately evaluated with chest radiography. However, when chest radiography does not allow identification of the location and nature of an area of increased opacity, ultrasonography (US) can help establish the diagnosis. US may be helpful in evaluation of persistent or unusual areas of increased opacity in the peripheral lung, pleural abnormalities, and mediastinal widening; US is particularly useful in patients with complete opacification of a hemithorax at radiography. In cases of pulmonary parenchymal lesions, identification of air or fluid bronchograms at US and of pulmonary vessels at color flow imaging is useful for differentiating pulmonary consolidation or atelectasis from lung masses and pleural lesions. US allows characterization of pleural fluid collections as simple, complicated, or fibroadhesive, which is important information for planning thoracentesis or thoracotomy. Computed tomography and magnetic resonance imaging are superior to US in evaluation of the mediastinum, but US is a reasonable alternative in certain situations (eg, to avoid unnecessary investigation of a normal thymus simulating a mediastinal mass). In cases of chest wall lesions, US may enable localization of the site of origin to soft tissues or an extrapleural intrathoracic location. Osseous involvement, particularly rib involvement, is easily evaluated with US.     

The value of thoracic computed tomography in the detection of recurrent Hodgkin's disease

Fifty chest radiographs and concurrent thoracic computed tomography (CT) scans obtained in a total of 44 patients with 50 separate episodes of suspected recurrent Hodgkin's disease were reviewed. Recurrent disease was present in 18 episodes, involving the mediastinum in 12, the lung parenchyma in five and both mediastinum and lung parenchyma in one. In four episodes, mediastinal recurrence was demonstrated on both the chest radiograph and CT scan. In a further two cases, the chest radiograph appeared normal but CT detected recurrence in the mediastinum. In 20 cases, the mediastinal appearances on chest radiography were suspicious but not diagnostic of recurrence, usually because of previous radiotherapy resulting in residual mediastinal widening. Computed tomography diagnosed recurrent disease which was subsequently proven in seven of these cases. Recurrent disease was suggested by CT in a further case, subsequently shown to be radiation fibrosis. Of the 12 remaining chest radiographs in which the mediastinal assessment was indeterminate, CT was true negative for recurrent disease in 10 cases and was also indeterminate in two. Recurrent disease in the lung parenchyma was demonstrated on the chest radiograph and CT scan on five occasions. There was one incident in which the chest radiograph was normal but CT detected recurrent parenchymal disease. The appearances of the lung parenchyma were indeterminate for recurrent disease on three chest radiographs but CT was helpful in only one case in which radiation change alone was diagnosed. In eight cases the diagnosis of recurrent disease by CT resulted in a decision to initiate treatment. Computed tomography is of value in detecting relapse in patients with suspected recurrent Hodgkin's disease when the chest radiograph is inconclusive, and may enable differentiation of radiation change from recurrent disease in the mediastinum.     

原发纵隔囊肿影像学表现

目的探讨原发纵隔囊肿影像表现特征,提高影像诊断的准确率。方法回顾性分析经手术病理证实且资料完整的42例原发纵隔囊肿的影像学表现。所有病例均摄胸部后前位与侧位片,胸部CT平扫29例,其中15例行增强扫描,胸部MRI平扫6例。观察病变的部位、大小、形态、密度(信号)、边缘、壁及其厚度、邻近结构。每一病种均分为影像征象典型与不典型2类。结果病变位于前纵隔28例,中、后纵隔各7例。上纵隔9例,中纵隔24例,下纵隔9例。支气管囊肿9例,囊性淋巴管瘤4例,胸腺囊肿11例,心包囊肿5例,成熟性囊性畸胎瘤13例。影像征象典型38例,不典型4例。结论90%的纵隔囊肿,根据CT、MRI显示的病变部位与内部密度、信号特征,可做出正确的影像诊断;不典型者确诊仍依靠手术病理。     

Malignant bilateral mediastinal teratoma: a case report]

The authors report a case of bilateral malignant teratoma of the mediastinum in a 40 year old female presenting with chest pain. Two separate bilateral soft tissue masses were noted in the mediastinum at imaging. On the right side, the mass was heterogeneous with large calcification and infiltration of the pericardium. On the left side, the mass was well defined, heterogeneous and without evidence of local invasion. The analysis of samples obtained by US guided puncture biopsy and surgical specimen of the two masses confirmed the diagnosis of pluricellular malignant teratoma. Mediastinal malignant teratomas represent 1 to 5% of all mediastinal tumors. To our knowledge, no case of synchronous bilateral mediastinal teratoma has never been reported.     

Radiographic evaluation of mediastinal lines as a diagnostic approach to occult or subtle mediastinal abnormalities

The mediastinal lines visible at conventional radiography represent the interfaces between the mediastinum and adjacent lung parenchyma. Preservation, obliteration, thickening and distortion of these lines represent the key to detecting and localising mediastinal abnormalities on chest radiographs. The learning objectives of this review are to: illustrate radiographic anatomy of the mediastinum with particular attention to mediastinal lines; describe radiographic signs that allow identification of mediastinal abnormalities that are difficult to detect on conventional chest radiographs; describe findings that help localise abnormalities in the anterior, middle or posterior mediastinum. The anterior junction line obliteration, the hilum overlay sign, the preservation of the posterior mediastinal lines and the silhouette sign with the right cardiac border are radiographic signs that allow identification and localisation of anterior mediastinal lesions. Widening of the right paratracheal stripe, distortion of the azygo-oesophageal recess and the convex border of the aortopulmonary window indicate the presence of a middle mediastinal abnormality. Thickening, distortion or disruption of paraortic and paraspinal lines and posterior junction line obliteration are caused by posterior mediastinal lesions. Knowledge of normal radiographic mediastinal anatomy and mediastinal lines is crucial to identifying subtle mediastinal abnormalities that can be easily missed on conventional radiography. Moreover, this approach allows identification of the involved mediastinal compartment on chest radiographs, thereby directing the most appropriate further diagnostic workup.     

Imaging findings of expansile lesions of the thymus

The purpose of this article is to review the imaging findings of the different expansile lesions of the thymus. Almost 50% of all mediastinal masses are located in the anterior mediastinum. The thymus is the most common site of origin of these masses. Several kinds of lesions can arise from this gland because it derives from the three embryonic germ cell layers. Primary neoplasms of the thymus are thymoma, thymolipomas, carcinoma, carcinoid, primary germ cell tumors, and lymphoma. The latter can also involve the organ in a secondary fashion. Other lesions that cause thymic enlargement and that can be confused with neoplasia are thymic cysts and thymic hyperplasia. Even though anterior mediastinal masses are first found on conventional radiographs, computed tomography and magnetic resonance are very useful additional studies for assessing the origin and extension of these masses. The basic concepts regarding embryology, anatomy, and histology relevant for the differential diagnosis of an enlarged thymic gland are also described.     

Initial ultrasound evaluation of an anterior mediastinal mass ultimately diagnosed as T-cell acute lymphoblastic leukemia: a report of three cases in children

Pediatric T-cell acute lymphoblastic leukemia (T-ALL) in the anterior mediastinum has an acute onset and requires early treatment. The diagnostic strategy for anterior mediastinal masses in pediatric patients usually involves imaging evaluation, surgical biopsy, or resection for diagnosis and treatment. Thereafter, appropriate chemotherapy regimen selection is based on the pathological diagnosis. In some cases, general anesthesia is avoided to prevent complications such as airway compression and circulatory collapse. We present 3 cases with T-ALL where ultrasound was used for the first evaluation of the anterior mediastinal mass. A 5-year-old girl had lymph node swelling at the supraclavicular fossa. Ultrasound examination showed a huge anterior mediastinal mass with an abnormal thymus, surrounding the proximal main trachea in the mediastinum. These sonographic findings indicated a possibility for tracheal compression during general anesthesia. A 12-year-old boy had dyspnea. Ultrasound examination showed a massive pericardial effusion and stenosis of the right pulmonary artery. These sonographic findings indicated a risk of circulation collapse. An 8-year-old boy had cervical swelling and dyspnea. Ultrasound examination showed a huge mass on the anterior mediastinum and a huge thrombus in the left atrium. This sonographic finding indicated a risk of thromboembolism. Ultrasonography is useful in pediatric patients with anterior mediastinal masses due to T-ALL. By focusing on the thymus, a diagnosis of T-ALL might be recommended. To avoid catastrophic circulation collapse, tracheal and vascular compression should be evaluated. Direct invasion may also be detectable.     

Prompt diagnosis and management of a ruptured mediastinal cystic teratoma

Mediastinal germ cell tumors are some of the less frequently encountered anterior mediastinal masses. We report an interesting case of a 26-year-old male with a ruptured mediastinal cystic teratoma. Initial plain radiograph and CT scan of the chest showed radiographic evidence of a ruptured cystic teratoma, including a peripherally enhancing, partially calcified mass with internal fat density. Upon surgical excision, the mass was found to adhere to the thymus and anterior aortic arch. The patient was promptly diagnosed via imaging and managed in a timely manner via complete surgical resection.     

Pictorial Review of Mediastinal Masses with an Emphasis on Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) has become a crucial tool for evaluating mediastinal masses considering that several lesions that appear indeterminate on computed tomography and radiography can be differentiated on MRI. Using a three-compartment model to localize the mass and employing a basic knowledge of MRI, radiologists can easily diagnose mediastinal masses. Here, we review the use of MRI in evaluating mediastinal masses and present the images of various mediastinal masses categorized using the International Thymic Malignancy Interest Group''s three-compartment classification system. These masses include thymic hyperplasia, thymic cyst, pericardial cyst, thymoma, mediastinal hemangioma, lymphoma, mature teratoma, bronchogenic cyst, esophageal duplication cyst, mediastinal thyroid carcinoma originating from ectopic thyroid tissue, mediastinal liposarcoma, mediastinal pancreatic pseudocyst, neurogenic tumor, meningocele, and plasmacytoma.     

The variable nature of the mediastinal contour lines: CT/chest radiography correlation

Interfacing of the lung with the mediastinum produces a number of mediastinal lines including those due to the innominate veins, left subclavian artery, paratracheal stripe, both anterior and posterior junction lines, the azygo-esophageal recess, descending aorta and paraspinal lines. Displacement or absence of one or more of these lines may be due to an abnormality of mediastinal contour or may indicate a mediastinal mass, but can occur in normal subjects. Correlative findings between chest radiography and chest computed tomography in 50 normal subjects illustrate the variable nature of these lines.     

Computer tomography of the anterior mediastinum in patients with myasthenia gravis and suspected thymoma.

Six patients with myasthenia gravis and suspected thymoma underwent radiologic investigation using plain chest radiography, conventional anterior mediastinal tomography, and computed tomography. All underwent exploratory thoractomy within 1 month of the radiologic workup. In three of the five cases that proved to be thymoma, CT yielded significant diagnostic information that bore directly on the management and/or prognosis of the patient. We therefore believe that CT may be a valuable adjunct in the radiologic investigation of the patient with myasthenia gravis.     

纵隔囊性病变的CT与MRI诊断

目的：探讨纵隔囊性病变的CT、MRI诊断及鉴别诊断。方法：回顾性总结30例经手术、病理确诊的纵隔囊性病变的CT及MRI表现，包括胸腺囊肿7例，囊性畸胎瘤8例，气管、支气管囊肿9例，食管囊肿4例，囊性淋巴管瘤2例。结果：不同纵隔囊性病变均有其较特定的发病部位。7例胸腺囊肿中6例位于前上纵隔的胸腺区，1例位于前纵隔中下部；8例囊性畸胎瘤主要位于前纵隔中部、大血管起始处；9例气管、支气管囊肿位于中上纵隔，气管、支气管右旁区；4例食管囊肿，其中3例位于后纵隔，1例位于中纵隔；2例囊性淋巴管瘤，其中1例为颈纵隔型，1例为颈一腋纵隔型。结论：纵隔囊性病变虽无明显特征性影像学表现，仔细观察CT与MRI征象特点，结合发病部位，对提高本病的诊断具有重要意义。     

Masses of the anterior mediastinum: CT and MR imaging

CT and MR imaging allow earlier diagnosis and more specific characterization of anterior mediastinal masses than is possible with plain film radiographs. This review describes state-of-the-art CT and MR imaging of the anterior mediastinum. After a discussion of CT and MR imaging and indications for their use, normal and abnormal CT and MR findings in the anterior mediastinum are reviewed. Abnormalities include benign and malignant neoplasms, cysts, and mediastinal thyroid. Several masses such as thymolipomas, goiters, cysts, and lymphangiomas often do not require removal and now can be diagnosed with reasonable accuracy when imaging results are combined with clinical history. Detection, diagnosis, staging, and follow-up of malignant anterior mediastinal masses are important and have been improved with CT and MR imaging.     

Imaging evaluation of pediatric mediastinal masses

Mediastinal masses in children are a heterogeneous group of asymptomatic to potentially life-threatening congenital, infectious, or neoplastic lesions that can present complex diagnostic and therapeutic dilemmas. This article presents the imaging features of the common mediastinal masses seen in the pediatric population. Classification of the masses is performed according to the traditional mediastinal compartment model, consisting of the anterior, middle, and posterior mediastinum. This scheme facilitates differentiation of the variety of disorders.     

Roentgenologic diagnosis of primary corticotropin-producing carcinoid tumors of the mediastinum

A study was undertaken of five patients with Cushing syndrome due to adrenocorticotropin (ACTH) production by thymic carcinoid tumor (primary mediastinal APUDomas), including two recent patients examined by computed tomography (CT) of the chest. Plain roentgenography of the chest initially failed to detect tumor in four of the five patients, while CT of the chest yielded definitive diagnostic information in both patients in whom it was employed. For one of these patients, a mediastinal tumor could be seen retrospectively on plain roentgenograms of the chest, although it had been missed on the first examination. One of the tumors appeared to be partially calcified on CT scan, a finding not previously reported. Blastic osseous metastasis, which is common when malignant carcinoid tumors spread to bone, was seen in one patient. Our data suggest that in patients with suspected ectopic ACTH production, CT scanning of the mediastinum should be performed early in order to avoid delay in diagnosis of an ACTH-secreting carcinoid tumor of the mediastinum.     

纵隔良性畸胎瘤的CT诊断（附29例分析）

目的评估CT对纵隔良性畸胎瘤的诊断价值.材料和方法回顾性分析经手术、病理证实29例纵隔良性畸胎瘤的CT表现.结果29例纵隔良性畸胎瘤中,位于前、中、上纵隔27例和前、中、下纵隔2例,囊性20例,囊实性7例和实性2例.肿瘤内含脂肪15例,钙化12例,侵犯邻近肺组织7例和胸腔积液4例.结论CT对纵隔良性畸胎瘤能准确定位和定性诊断.