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Radiation therapy is one of the cornerstones for the treatment of thoracic malignancies. Although advances in radiation therapy technology have improved the delivery of radiation considerably, adverse effects are still common. Postirradiation changes affect the organ or tissue treated and the neighboring structures. Advances in external-beam radiation delivery techniques and how these techniques affect the expected thoracic radiation-induced changes are described. In addition, how to distinguish these expected changes from complications such as infection and radiation-induced malignancy, and identify treatment failure, that is, local tumor recurrence, is reviewed. © RSNA, 2019.

Leukemias are malignancies in which abnormal white blood cells are produced in the bone marrow, resulting in compromise of normal bone marrow hematopoiesis and subsequent cytopenias. Leukemias are classified as myeloid or lymphoid depending on the type of abnormal cells produced and as acute or chronic according to cellular maturity. The four major types of leukemia are acute myeloid leukemia, chronic myeloid leukemia, acute lymphoblastic leukemia, and chronic lymphocytic leukemia. Clinical manifestations are due to either bone marrow suppression (anemia, thrombocytopenia, or neutropenia) or leukemic organ infiltration. Imaging manifestations of leukemia in the thorax are myriad. While lymphadenopathy is the most common manifestation of intrathoracic leukemia, leukemia may also involve the lungs, pleura, heart, and bones and soft tissues. Myeloid sarcomas occur in 5%-7% of patients with acute myeloid leukemia and represent masses of myeloid blast cells in an extramedullary location. © RSNA, 2019.

Primary lung tumors in children are rare, with a narrow range of diagnostic considerations. However, the overlapping imaging appearances of these tumors necessitate attention to key discriminating imaging and pathologic features. In the neonate and infant, the important considerations include pleuropulmonary blastoma (PPB), infantile fibrosarcoma, and fetal lung interstitial tumor. Among these tumors, imaging findings such as air-filled cysts in type 1 PPB and homogeneously low attenuation of fetal lung interstitial tumors are relatively specific. Key pathologic and genetic discriminators among this group of tumors include the DICER1 germline mutation found in PPB and the t(12,15)(p13;q25) translocation and ETV6-NTRK3 fusion gene seen in infantile fibrosarcoma. Primary lung tumors in older children include inflammatory myofibroblastic tumors (IMTs), carcinoid salivary gland-type tumors of the lung, recurrent respiratory papillomatosis, and other rare entities. IMT, a spindle-cell proliferation with inflammatory elements, is the most common lung tumor in children. Anaplastic lymphoma kinase, a receptor-type protein tyrosine kinase, is present in 50% of these tumors, and this finding may support an imaging diagnosis of IMT. Carcinoid tumors account for a substantial portion of childhood lung tumors, and their characteristic avid enhancement on images corresponds to the compressed fibrovascular stroma histologically. Furthermore, novel imaging agents used with somatostatin receptor analogs have an emerging role in the evaluation of carcinoid tumors. Although less common than mucoepidermoid carcinoma, adenoid cystic carcinoma tends to recur given the perineural spread seen histologically. Integrating radiologic and pathologic knowledge is critical to accurate diagnosis, treatment planning, and surveillance of primary lung tumors in children.

Lung cancer remains the leading cause of cancer-related mortality worldwide. To formulate effective treatment strategies and optimize patient outcomes, accurate staging is essential. Lung cancer staging has traditionally relied on a TNM staging system, for which the International Association for the Study of Lung Cancer (IASLC) has recently proposed changes. The revised classification for this eighth edition of the TNM staging system (TNM-8) is based on detailed analysis of a new large international database of lung cancer cases assembled by the IASLC for the purposes of this project. Fundamental changes incorporated into TNM-8 include (a) modifications to the T classification on the basis of 1-cm increments in tumor size; (b) grouping of lung cancers that result in partial or complete lung atelectasis or pneumonitis; (c) grouping of tumors with involvement of a main bronchus irrespective of distance from the carina; (d) reassignment of diaphragmatic invasion in terms of T classification; (e) elimination of mediastinal pleural invasion from the T classification; and (f) subdivision of the M classification into different descriptors on the basis of the number and site of extrathoracic metastases. In response to these revisions, established stage groups have been modified, and others have been created. In addition, recommendations for classifying patterns of disease that result in multiple sites of pulmonary involvement, including multiple primary lung cancers, lung cancers with separate tumor nodules, multiple ground-glass/lepidic lesions, and consolidation, as well as recommendations for lesion measurement, are addressed. Understanding the key revisions introduced in TNM-8 allows radiologists to accurately stage patients with lung cancer and optimize therapy. © RSNA, 2018.

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.

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.

Neoplasms of the chest wall are uncommon lesions that represent approximately 5% of all thoracic malignancies. These tumors comprise a heterogeneous group of neoplasms that may arise from osseous structures or soft tissues, and they may be malignant or benign. More than 50% of chest wall neoplasms are malignancies and include tumors that may arise as primary malignancies or secondarily involve the chest wall by way of direct invasion or metastasis from intrathoracic or extrathoracic neoplasms. Although 20% of chest wall tumors may be detected at chest radiography, chest wall malignancies are best evaluated with cross-sectional imaging, principally multidetector computed tomography (CT) and magnetic resonance (MR) imaging, each of which has distinct strengths and limitations. Multidetector CT is optimal for depicting bone, muscle, and vascular structures, whereas MR imaging renders superior soft-tissue contrast and spatial resolution and is better for delineating the full extent of disease. Fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT is not routinely performed to evaluate chest wall malignancies. The primary functions of PET/CT in this setting include staging of disease, evaluation of treatment response, and detection of recurrent disease. Ultrasonography has a limited role in the evaluation and characterization of superficial chest wall lesions; however, it can be used to guide biopsy and has been shown to depict chest wall invasion by lung cancer more accurately than CT. It is important that radiologists be able to identify the key multidetector CT and MR imaging features that can be used to differentiate malignant from benign chest lesions, suggest specific histologic tumor types, and ultimately guide patient treatment. (©)RSNA, 2016.

Small cell lung carcinoma (SCLC) is the most common primary pulmonary neuroendocrine malignancy and is characterized by a rapid doubling time and high growth fraction. Approximately 60%-70% of patients present with metastatic disease at the time of diagnosis, and their prognosis is poor. However, improved survival has been demonstrated when SCLC is diagnosed early and specific treatment strategies are used. A modified version of the Veterans Administration Lung Cancer Study Group (VALSG) staging system has traditionally been used to categorize SCLC as limited-stage or extensive-stage disease to guide therapy. However, the International Association for the Study of Lung Cancer has recommended that the current seventh edition of the American Joint Committee on Cancer tumor-node-metastasis staging system for lung cancer replace the VALSG system for staging of SCLC. Appropriate staging and patient management require knowledge of imaging manifestations of SCLC across multiple imaging modalities, the strengths and weaknesses of specific examinations, the correlation of these findings with the staging criteria used in clinical practice, and the impact of appropriate staging on patient treatment and survival. Computed tomography (CT) is primarily used to evaluate the primary tumor and the extent of intrathoracic disease. In recent years, however, 2-[fluorine-18]fluoro-2-deoxy-d-glucose positron emission tomography/CT has proved to be more accurate than conventional imaging in the staging of SCLC and can be used to guide therapy and assess treatment response.

Malignant pleural mesothelioma (MPM) is the most common primary malignancy of the pleura and is associated with asbestos exposure in approximately 80% of patients. The patient prognosis is poor, with a median survival of 9-17 months after diagnosis. However, improved survival and decreased morbidity and mortality have been demonstrated when the diagnosis is made in the early stages of disease and specific treatment strategies are implemented. A staging system that focuses on the extent of primary tumor (T), lymph node involvement (N), and metastatic disease (M) has been devised by the International Mesothelioma Interest Group and emphasizes factors related to overall survival. Radiologists should recognize the manifestations of MPM across multiple imaging modalities, translate these findings into the updated staging system, and understand the effects of appropriate staging on treatment and survival. Computed tomography (CT) remains the primary imaging modality used to evaluate MPM and efficiently demonstrates the extent of primary tumor, intrathoracic lymphadenopathy, and extrathoracic spread. However, additional imaging modalities, such as magnetic resonance (MR) imaging of the thorax and positron emission tomography (PET)/CT with fluorodeoxyglucose, have emerged in recent years and are complementary to CT for disease staging and evaluation of patients with MPM. Thoracic MR imaging is particularly useful for identifying invasion of the chest wall, mediastinum, and diaphragm, and PET/CT can accurately demonstrate intrathoracic and extrathoracic lymphadenopathy and metastatic disease.

Purpose: To determine whether there is a sex difference in the appearance of the normal thymus in 20-30-year-old men and women., Materials and Methods: This retrospective study was approved by the institutional review board and was compliant with HIPAA. The requirement for informed consent was waived. Images and medical records of 238 consecutive subjects without known thymic disease (175 men, 63 women) who underwent chest computed tomography with intravenous contrast material in 2008 were reviewed. Average thymic region of interest (ROI), subjective assessment of thymic attenuation by using a scale of grades 0-3, thymic anteroposterior measurement, and mean maximal thymic lobe thickness were recorded by two independent thoracic radiologists, blinded to subject age and sex. Thymic morphologic characteristics were assessed in consensus. The two-sided Wilcoxon rank-sum test, Student t test, test for linear regression, analysis of covariance, two-way factorial analysis of variance, and continuity-adjusted χ(2) test were used for statistical analysis., Results: There was a significant sex difference in thymic attenuation as measured objectively by using mean thymic ROI measurement (P < .0001) and subjectively by using a scale of grades 0-3 (P < .0001), which held true when corrected for age (P < .0001). A sex difference was also found in regard to the rate of decrease in mean thymic attenuation with age, with men's thymuses exhibiting a significant decrease in attenuation during the decade, unlike women (P = .0479). There was no significant sex difference in mean maximal thymic lobe thickness (P = .8697). A quadrilateral, as opposed to triangular, configuration of the thymus was more common in women than men (P = .0034)., Conclusion: There is a significant sex difference in normal thymic appearance in 20-30-year-old men and women. The thymus of 20-30-year-old women typically exhibits higher attenuation and more commonly exhibits a quadrilateral configuration.