Imaging Patterns of Pneumonia.

Imaging findings of pneumonia are diverse, with frequent overlap between the various infectious etiologies of pneumonia, as well as various other disease conditions, including inflammatory conditions, vasculitis, and malignancy. In the appropriate clinical context, a number of imaging findings and the patterns that they form on imaging may provide clues that enable radiologists and clinicians to narrow the differential diagnostic considerations. Although a definite diagnosis can rarely be provided based on imaging findings alone, the combination of clinical, imaging, and laboratory findings are usually sufficient for accurate diagnosis and management decisions. It is important for radiologists to recognize the wide variety of imaging patterns that occur with different causes of pneumonia, and recognize specific imaging signs of certain infections when present, thereby facilitating diagnosis and optimizing patient care.

Imaging of the Anterior/Prevascular Mediastinum.

Prevascular mediastinal masses include a wide range of benign and malignant entities. Localization of mediastinal masses to specific compartments together with characteristic imaging findings and demographic and clinical information allows formulation of a focused differential diagnosis. Radiologists may use these methods to distinguish between surgical and nonsurgical cases and thus inform patient management and have an impact on outcomes. Treatment of choice varies based on the pathology, ranging from no intervention or serial imaging follow-up to surgical excision, chemotherapy, and/or radiation.

Uncommon thoracic manifestations from extrapulmonary tumors: Computed tomography evaluation - Pictorial review.

Although metastasis can occur at a variety of sites, pulmonary involvement is common in patients with cancer. Depending on the source and type of tumor, pulmonary metastases present with a wide range of radiologic appearances. Hematogenous dissemination through the pulmonary arteries to the pulmonary capillary network is the most common form of spread in pulmonary metastases. However, they may also reach the lung via lymphatic dissemination, secondary airway involvement, vessel tumor embolism, and direct chest invasion. In the evaluation of patients with known extrathoracic tumors, CT is the state-of-the-art imaging modality for detecting and characterize pulmonary metastases as well as to predict resectability. Although CT limitations are well known, knowledge of growth rates of various tumors and understanding the pattern of spread may be helpful clues in suggesting and even establish the specific diagnosis. The purpose of this pictorial review is to discuss the imaging appearances of different patterns of intrathoracic tumoral dissemination.

Multimodality Imaging of Focal and Diffuse Fibrosing Mediastinitis.

Fibrosing mediastinitis is a rare benign but potentially life-threatening process that occurs because of proliferation of fibrotic tissue in the mediastinum. The focal subtype is more common and typically is associated with an abnormal immunologic response to Histoplasma capsulatum infection. Affected patients are typically young at presentation, but a wide age range has been reported, without a predilection for either sex. The diffuse form may be idiopathic or associated with autoimmunity, usually affects middle-aged and/or elderly patients, and is more common in men. For both subtypes, patients present with signs and symptoms related to obstruction or compression of vital mediastinal structures. The most common presenting signs and symptoms are cough, dyspnea, recurrent pneumonia, hemoptysis, and pleuritic chest pain. Patients with the diffuse subtype may have additional extrathoracic symptoms depending on the other organ systems involved. Because symptom severity is variable, treatment should be individualized with therapies tailored to alleviate compression of the affected mediastinal structures. Characteristic imaging features of fibrosing mediastinitis include infiltrative mediastinal soft tissue (with or without calcification) with compression or obstruction of mediastinal vascular structures and/or the aerodigestive tract. When identified in the appropriate clinical setting, these characteristic features allow the radiologist to suggest the diagnosis of fibrosing mediastinitis. Careful assessment is crucial at initial and follow-up imaging for exclusion of underlying malignancy, assessment of disease progression, identification of complications, and evaluation of treatment response. Online supplemental material is available for this article. ©RSNA, 2019.

Evaluation after Orthotopic Heart Transplant: What the Radiologist Should Know.

Orthotopic heart transplant (OHT) is the treatment of choice for end-stage heart disease. As OHT use continues and postoperative survival increases, multimodality imaging evaluation of the transplanted heart will continue to increase. Although some of the imaging is performed and interpreted by cardiologists, a substantial proportion of images are read by radiologists. Because there is little to no consensus on a systematic approach to patients after OHT, radiologists must become familiar with common normal and abnormal posttreatment imaging features. Intrinsic transplant-related complications may be categorized on the basis of time elapsed since transplant into early (0-30 days), intermediate (1-12 months), and late (>12 months) stages. Although there can be some overlap between stages, it remains helpful to consider the time elapsed since surgery, because some complications are more common at certain stages. Recognition of differing OHT surgical techniques and their respective postoperative imaging features helps to avoid image misinterpretation. Expected early postoperative findings include small pneumothoraces, pleural effusions, pneumomediastinum, pneumopericardium, postoperative atelectasis, and an enlarged cardiac silhouette. Early postoperative complications also can include sternal dehiscence and various postoperative infections. The radiologist's role in the evaluation of allograft failure and rejection, endomyocardial biopsy complications, cardiac allograft vasculopathy, and posttransplant malignancy is highlighted. Because clinical manifestations of disease may be delayed in transplant recipients, radiologists often recognize postoperative complications on the basis of imaging and may be the first to suggest a specific diagnosis and thus positively affect patient outcomes. Online supplemental material is available for this article. ©RSNA, 2019.

IASLC/ITMIG Staging System and Lymph Node Map for Thymic Epithelial Neoplasms.

Thymic epithelial neoplasms are rare malignancies that arise from the thymus and include thymoma, thymic carcinoma, and thymic neuroendocrine tumors. At least 15 different stage classifications have been proposed for thymic epithelial neoplasms and used to varying degrees in clinical practice, many of which have been constructed from small groups of patients. Traditionally, the Masaoka and Masaoka-Koga staging systems have been the schemes most commonly employed, and the latter has been recommended for use by the International Thymic Malignancy Interest Group (ITMIG). An official, consistent stage classification system has recently been recognized by the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC), which are responsible for defining stage classifications for neoplasms. To establish this stage classification system, the International Association for the Study of Lung Cancer (IASLC) and ITMIG amassed a large retrospective database and evaluated this group of cases to develop proposals for the eighth edition of the stage classification manuals. For this endeavor, IASLC provided funding and statistical analysis and ITMIG provided the involvement of the clinicians and researchers actively participating in the study of thymic epithelial neoplasms. To accomplish this, a Thymic Domain of the Staging and Prognostic Factors Committee (TD-SPFC) was established to formulate the rationale, methodology, and definitions of this tumor-node-metastasis (TNM) staging system, which is presented in this article. © RSNA, 2017.

ITMIG Classification of Mediastinal Compartments and Multidisciplinary Approach to Mediastinal Masses.

Division of the mediastinum into specific compartments is beneficial for a number of reasons, including generation of a focused differential diagnosis for mediastinal masses identified on imaging examinations, assistance in planning for biopsies and surgical procedures, and facilitation of communication between clinicians in a multidisciplinary setting. Several classification schemes for the mediastinum have been created and used to varying degrees in clinical practice. Most radiology classifications have been based on arbitrary landmarks outlined on the lateral chest radiograph. A new scheme based on cross-sectional imaging, principally multidetector computed tomography (CT), has been developed by the International Thymic Malignancy Interest Group (ITMIG) and accepted as a new standard. This clinical division scheme defines unique prevascular, visceral, and paravertebral compartments based on boundaries delineated by specific anatomic structures at multidetector CT. This new definition plays an important role in identification and characterization of mediastinal abnormalities, which, although uncommon and encompassing a wide variety of entities, can often be diagnosed with confidence based on location and imaging features alone. In other scenarios, a diagnosis may be suggested when radiologic features are combined with specific clinical information. In this article, the authors present the new multidetector CT-based classification of mediastinal compartments introduced by ITMIG and a structured approach to imaging evaluation of mediastinal abnormalities. ©RSNA, 2017.

Emerging Concepts in Intramural Hematoma Imaging.

Intramural hematoma (IMH) is included in the spectrum of acute aortic syndrome and appears as an area of hyperattenuating crescentic thickening in the aortic wall that is best seen at nonenhanced computed tomography. IMH is historically believed to originate from ruptured vasa vasorum in the aortic media without an intimal tear, but there are reports of small intimomedial tears identified prospectively at imaging or found at surgery in some cases of IMH. These reports have blurred the distinction between aortic dissection and IMH and raise questions about what truly distinguishes the entities that compose acute aortic syndrome. The pathophysiology of these subgroups and the controversies surrounding their differentiation are discussed. The natural history of IMH is highly variable; it may resolve or progress to aneurysm, dissection, or rupture. The authors review various imaging prognostic factors that should be reported by the radiologist, including Stanford classification, maximum aortic diameter, maximum IMH thickness, focal contrast enhancement (including ulcerlike projection and intramural blood pool), and pleural or pericardial effusion. Medical (nonsurgical) versus surgical treatment strategies depend primarily on the Stanford classification, although more recent studies of Asian cohorts report success of initial medical treatment in patients with Stanford type A IMH, with timed (delayed) surgery for patients who develop complications. Understanding the imaging appearance and prognostic factors of IMH helps the radiologist and surgeon identify patients at greatest risk for complications to ensure appropriate treatment and improve patient outcomes. (©)RSNA, 2016.

Thoracic Metastases From Primary Hepatobiliary and Pancreatic Malignancies: Predictable Patterns of Metastatic Spread.

This article reviews common and uncommon patterns of thoracic metastatic disease in primary hepatobiliary and pancreatic malignancies that are often overlooked or improperly diagnosed because of atypical location or imaging appearance. An understanding of the pathophysiology and routes of tumor spread aids in tailoring a search pattern allowing for more accurate evaluation of disease activity.

A modern definition of mediastinal compartments.

Division of the mediastinum into compartments is used to help narrow the differential diagnosis of newly detected mediastinal masses, to assist in planning biopsy and surgical procedures, and to facilitate communication among clinicians of multiple disciplines. Several traditional mediastinal division schemes exist based upon arbitrary landmarks on the lateral chest radiograph. We describe a modern, computed tomography-based mediastinal division scheme, which has been accepted by the International Thymic Malignancy Interest Group as a new standard. This clinical classification defines a prevascular (anterior), a visceral (middle), and a paravertebral (posterior) compartment, with anatomic boundaries defined clearly by computed tomography. It is our intention that this definition be used in the reporting of clinical cases and the design of prospective clinical trials.

Imaging features of thoracic metastases from gynecologic neoplasms.

Gynecologic malignancies are a heterogeneous group of common neoplasms and represent the fourth most common malignancy in women. Thoracic metastases exhibit various imaging patterns and are usually associated with locally invasive primary neoplasms with intra-abdominal spread. However, thoracic involvement may also occur many months to years after initial diagnosis or as an isolated finding in patients without evidence of intra-abdominal neoplastic involvement. Thoracic metastases from endometrial carcinoma typically manifest as pulmonary nodules and lymphadenopathy. Thoracic metastases from ovarian cancer often manifest with small pleural effusions and subtle pleural nodules. Thoracic metastases to the lungs, lymph nodes, and pleura may also exhibit calcification and mimic granulomatous disease. Metastases from fallopian tube carcinomas exhibit imaging features identical to those of ovarian cancers. Most cervical cancers are of squamous histology, and while solid pulmonary metastases are more common, cavitary metastases occur with some frequency. Metastatic choriocarcinoma to the lung characteristically manifests with solid pulmonary nodules. Some pulmonary metastases from gynecologic malignancies exhibit characteristic features such as cavitation (in squamous cell cervical cancer) and the "halo" sign (in hemorrhagic metastatic choriocarcinoma) at computed tomography (CT). However, metastases from common gynecologic malignancies may be subtle and indolent and may mimic benign conditions such as intrapulmonary lymph nodes and remote granulomatous disease. Therefore, radiologists should consider the presence of locoregional disease as well as elevated tumor marker levels when interpreting imaging studies because subtle imaging findings may represent metastatic disease. Positron emission tomography/CT may be helpful in identifying early locoregional and distant tumor spread.

Spectrum of pulmonary neuroendocrine proliferations and neoplasms.

Neuroendocrine neoplasms are ubiquitous tumors found throughout the body, most commonly in the gastrointestinal tract followed by the thorax. Neuroendocrine cells occur normally in the bronchial and bronchiolar epithelium and may be solitary or may occur in clusters. Although neuroendocrine cell proliferations may be found in association with chronic lung disease, a broad range of neuroendocrine proliferations and neoplasms may occur and exhibit variable biologic behavior. Diffuse idiopathic neuroendocrine cell hyperplasia (DIPNECH) is a diffuse idiopathic form of neuroendocrine cell hyperplasia and is considered a preinvasive lesion that may give rise to carcinoid tumors. Patients with DIPNECH are typically older women who may be asymptomatic or may present with chronic respiratory symptoms. DIPNECH manifests as multifocal bilateral pulmonary micronodules on expiratory high-resolution computed tomographic (CT) images; the air trapping is secondary to constrictive bronchiolitis. Carcinoid tumors are low-grade malignant neoplasms that typically affect symptomatic children and young adults. Carcinoids manifest as well-defined pulmonary nodules or masses that are often closely related to central bronchi. They may exhibit intrinsic calcification and contrast material enhancement at CT, and patients with carcinoids may have postobstructive atelectasis and pneumonia. Although typical carcinoids are indolent neoplasms and patients have a good prognosis, atypical carcinoids are aggressive malignancies with a propensity for metastasis. Both are optimally treated with complete surgical excision. Large cell neuroendocrine carcinoma and small cell lung cancer are highly aggressive neuroendocrine malignancies that usually affect elderly smokers. These tumors manifest with large peripheral or central pulmonary masses. Local invasion, intrathoracic lymphadenopathy, and distant metastases are frequent at presentation. As a result, affected patients may not be candidates for surgical resection, are often treated with chemotherapy with or without radiation, and have a poor prognosis.

Role of imaging in the diagnosis, staging, and treatment of thymoma.

Thymoma is a rare mediastinal neoplasm but is the most common primary neoplasm of the anterior mediastinum. There have been only a few published reports assessing this disease. Furthermore, many of these reports are from a single institution and span several decades, which may lead to potentially misleading conclusions related to diagnosis, staging, and treatment. Computed tomography is the imaging modality of choice for evaluating thymoma and can help distinguish thymoma from other anterior mediastinal abnormalities. Tumor stage and extent of resection are the most important prognostic factors. Tumors that are encapsulated and are amenable to complete resection have a good prognosis, whereas invasive and unresectable tumors have a poor prognosis regardless of their histologic characteristics. Radiologists must be aware of the full spectrum of imaging findings of thymoma, the standard guidelines for diagnostic evaluation, and how imaging findings affect therapeutic decisions.

Imaging findings in human Bordetella bronchiseptica pneumonia.

Bordetella bronchiseptica is a gram-negative coccobacillus, which causes respiratory infection in dogs, rabbits, and pigs, and is rarely a human pulmonary pathogen. We present 2 immunocompromised patients diagnosed with B. bronchiseptica pneumonia. To our knowledge, these are the first reports of this disease in patients with B-cell lymphoma and an orthotopic cardiac transplant. In this report, we briefly discuss the epidemiology, microbiology, and challenges in the laboratory identification of B. bronchiseptica and describe the protean imaging manifestations of this rare pulmonary infection. We also address issues related to treatment and prognosis.

Primary aortic myxofibrosarcoma mimicking thrombus: findings on CT, MRI, and angiography.

Aortic sarcoma is a rare vascular malignancy. We report a case of primary aortic myxofibrosarcoma mimicking thrombus. This neoplasm demonstrated no contrast enhancement on computed tomography or magnetic resonance imaging and was clinically suspected to represent a large thrombus, although aortic primary neoplasm was considered in the differential diagnosis on the basis of imaging. Biopsies of the aortic lesion and a concurrent brain lesion were consistent with the diagnosis of aortic myxofibrosarcoma with brain metastasis. This report highlights overlapping imaging features between primary aortic sarcoma and vascular thrombus and the importance of considering neoplastic conditions in the differential diagnosis of large intravascular soft tissue lesions.

Rebound thymic hyperplasia after pneumonectomy and chemotherapy for primary synovial sarcoma.

Thymic hyperplasia occurs in a small proportion of patients receiving chemotherapy for various malignancies. It likely results from an immunologic rebound phenomenon. Fluorodeoxyglucose positron emission tomography-computed tomography is an important tool for staging malignant neoplasms. We report a case of rebound thymic hyperplasia manifesting as a hypermetabolic mass on fluorodeoxyglucose positron emission tomography-computed tomography after pneumonectomy and chemotherapy for primary pulmonary synovial sarcoma. We highlight the importance of recognizing the phenomenon of rebound thymic hyperplasia, as it can mimic residual or recurrent malignancy, especially in the setting of altered chest anatomy.

Imaging of thymic epithelial neoplasms.

Thymic epithelial neoplasms are uncommon lesions. Affected patients may be asymptomatic or may present with thoracic complaints or paraneoplastic syndromes. Asymptomatic lesions may be discovered incidentally during chest radiography or during other chest imaging studies. This article addresses the imaging evaluation of patients who have thymic epithelial neoplasms, specifically covering the use of chest radiography, CT, MRI, and positron emission tomography.