RadioGraphics Update: The Ninth Edition TNM Staging System for Thymic Epithelial Tumors.

Editor's Note.-RadioGraphics Update articles supplement or update information found in full-length articles previously published in RadioGraphics. These updates, written by at least one author of the previous article, provide a brief synopsis that emphasizes important new information such as technological advances, revised imaging protocols, new clinical guidelines involving imaging, or updated classification schemes.

The Role of Chest Radiography in Lung Cancer.

Chest radiography is one of the most commonly performed imaging tests, and benefits include accessibility, speed, cost, and relatively low radiation exposure. Lung cancer is the third most common cancer in the United States and is responsible for the most cancer deaths. Knowledge of the role of chest radiography in assessing patients with lung cancer is important. This article discusses radiographic manifestations of lung cancer, the utility of chest radiography in lung cancer management, as well as the limitations of chest radiography and when computed tomography (CT) is indicated.

Imaging of Lung Cancer Staging: TNM 9 Updates.

Imaging plays a key role in clinical staging of lung cancer and guiding therapy. A thorough understanding of the staging system including the nomenclature and updates is necessary to tailor treatment plans and optimize patient care. The 9th edition of the Tumor, Node, Metastasis staging system for lung cancer has no changes for T classification and subdivides N2 and M1c categories. In nodal staging, N2 splits into N2a, ipsilateral mediastinal single station involvement and N2b, ipsilateral mediastinal multiple stations involvement. In the staging of multiple extrathoracic metastases, M1c splits into M1c1, multiple extrathoracic metastases in one organ system and M1c2, multiple extrathoracic metastases in multiple organ systems. Awareness of the proposed changes in TNM-9 staging classification is essential to provide methodical and accurate imaging interpretation.

Pitfalls in Positron Emission Tomography/Computed Tomography in the Thorax and Abdomen.

Positron emission tomography/computed tomography (PET/CT) using [18F]-fluoro-2-deoxy-D-glucose (FDG) has become the mainstay imaging modality for evaluating oncology patients with certain cancers. The most common FDG PET/CT applications include staging/restaging, assessing response to therapy and detecting tumor recurrence. It is important to be aware of potential pitfalls and technical artifacts on PET/CT in the chest and abdomen to ensure accurate interpretation, avoid unnecessary intervention and optimize patient care.

Imaging in Lung Cancer Staging.

Lung cancer remains one of the leading causes of mortality worldwide, as well as in the United States. Clinical staging, primarily with imaging, is integral to stratify patients into groups that determine treatment options and predict survival. The eighth edition of the tumor, node, metastasis (TNM-8) staging system proposed in 2016 by the International Association for the Study of Lung Cancer remains the current standard for lung cancer staging. The system is used for all subtypes of lung cancer, including non-small cell lung cancer, small cell lung cancer, and bronchopulmonary carcinoid tumors.

Pericardial Recesses on Computed Tomography: Implications for the Pulmonologist.

The pericardium comprises a double-walled fibrous-serosal sac that encloses the heart. Reflections of the serosal layer form sinuses and recesses. With advances in multidetector computed tomography (CT) technology, pericardial recesses are frequently detected with thin-section CT. Knowledge of pericardial anatomy on imaging is crucial to avoid misinterpretation of fluid-filled pericardial sinuses and recesses as adenopathy/pericardial metastasis or aortic dissection, which can impact patient management and treatment decisions. The authors offer a comprehensive review of pericardial anatomy and its variations observed on CT, potential pitfalls in image interpretation, and implications for the pulmonologist with respect to unnecessary diagnostic procedures or interventions.

Drug-induced Lung Disease in the Oncology Patient: From Cytotoxic Agents to Immunotherapy.

Drug-induced lung disease is commonly encountered, especially in the oncology setting. Diagnosis is challenging because clinical and radiologic findings are nonspecific, often overlapping with other lung pathologies in these patients due to underlying neoplasia, infection, or other treatment effects such as radiotherapy. Furthermore, oncology patients often receive multiple antineoplastic agents concurrently, and virtually every agent has an association with lung injury. In this article, we will review a variety of antineoplastic agents that are associated with drug-induced injury and discuss incidence, their typical timing of onset, and imaging features.

Thymic Imaging Pitfalls and Strategies for Optimized Diagnosis.

Thymic imaging is challenging because the imaging appearance of a variety of benign and malignant thymic conditions are similar. CT is the most commonly used modality for mediastinal imaging, while MRI and fluorine 18 fluorodeoxyglucose (FDG) PET/CT are helpful when they are tailored to the correct indication. Each of these imaging modalities has limitations and technical pitfalls that may lead to an incorrect diagnosis and mismanagement. CT may not be sufficient for the characterization of cystic thymic processes and differentiation between thymic hyperplasia and thymic tumors. MRI can be used to overcome these limitations but is subject to other potential pitfalls such as an equivocal decrease in signal intensity at chemical shift imaging, size limitations, unusual signal intensity for cysts, subtraction artifacts, pseudonodularity on T2-weighted MR images, early imaging misinterpretation, flow and spatial resolution issues hampering assessment of local invasion, and the overlap of apparent diffusion coefficients between malignant and benign thymic entities. FDG PET/CT is not routinely indicated due to some overlap in FDG uptake between thymomas and benign thymic processes. However, it is useful for staging and follow-up of aggressive tumors (eg, thymic carcinoma), particularly for detection of occult metastatic disease. Pitfalls in imaging after treatment of thymic malignancies relate to technical challenges such as postthymectomy sternotomy streak metal artifacts, differentiation of postsurgical thymic bed changes from tumor recurrence, or human error with typical "blind spots" for identification of metastatic disease. Understanding these pitfalls enables appropriate selection of imaging modalities, improves diagnostic accuracy, and guides patient treatment. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Lung Cancer Staging: Imaging and Potential Pitfalls.

Lung cancer is the leading cause of cancer deaths in men and women in the United States. Accurate staging is needed to determine prognosis and devise effective treatment plans. The International Association for the Study of Lung Cancer (IASLC) has made multiple revisions to the tumor, node, metastasis (TNM) staging system used by the Union for International Cancer Control and the American Joint Committee on Cancer to stage lung cancer. The eighth edition of this staging system includes modifications to the T classification with cut points of 1 cm increments in tumor size, grouping of lung cancers associated with partial or complete lung atelectasis or pneumonitis, grouping of tumors with involvement of a main bronchus regardless of distance from the carina, and upstaging of diaphragmatic invasion to T4. The N classification describes the spread to regional lymph nodes and no changes were proposed for TNM-8. In the M classification, metastatic disease is divided into intra- versus extrathoracic metastasis, and single versus multiple metastases. In order to optimize patient outcomes, it is important to understand the nuances of the TNM staging system, the strengths and weaknesses of various imaging modalities used in lung cancer staging, and potential pitfalls in image interpretation.

Approach to Imaging of Mediastinal Masses.

Mediastinal masses present a diagnostic challenge due to their diverse etiologies. Accurate localization and internal characteristics of the mass are the two most important factors to narrow the differential diagnosis or provide a specific diagnosis. The International Thymic Malignancy Interest Group (ITMIG) classification is the standard classification system used to localize mediastinal masses. Computed tomography (CT) and magnetic resonance imaging (MRI) are the two most commonly used imaging modalities for characterization of the mediastinal masses.

Spectrum of Imaging Patterns of Lung Cancer following Radiation Therapy.

Radiation therapy using conventional or newer high-precision dose techniques, including three-dimensional conformal radiotherapy, intensity-modulated radiation therapy, stereotactic body radiation therapy, four-dimensional conformational radiotherapy, and proton therapy, is an important component of treating patients with lung cancer. Knowledge of the radiation technique used and the expected temporal evolution of radiation-induced lung injury, as well as patient-specific parameters such as previous radiotherapy, concurrent chemoradiotherapy, or immunotherapy, is important in image interpretation. This review discusses factors that affect the development and severity of radiation-induced lung injury and its radiological manifestations, as well as the differences between conventional and high-precision dose radiotherapy techniques.

Imaging evaluation of thymic tumors.

An integral part of managing patients with thymoma and thymic carcinoma is imaging. At diagnosis and staging, imaging helps demonstrate the extent of local invasion and distant metastases which allows the proper stratification of patients for therapy. For decades, the predominant staging system for thymic tumors was the Masaoka-Koga staging system. More recently, however, the International Association for the Study of Lung Cancer, the International Thymic Malignancies Interest Group (ITMIG), the European Society of Thoracic Surgeons, the Chinese Alliance for Research on Thymomas, and the Japanese Association of Research on Thymus partnered together to develop a tumor-node-metastasis (TNM) staging system specifically for thymic tumors based on a retrospective database of nearly 10,000 patients. The TNM 8th edition defines specific criteria for thymic tumors. Imaging also serves to assess treatment response and detect recurrent disease after various treatment modalities. The Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 is currently used to assess response to treatment. ITMIG recommends certain modifications to RECIST version 1.1, however, in thymic tumors due to unique patterns of spread. While there is often overlap, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography/computed tomography (PET/CT) characteristics can help differentiate thymoma and thymic carcinoma, with newer CT and MRI techniques under evaluation showing encouraging potential.

Multimodality imaging of mediastinal masses and mimics.

A wide variety of neoplastic and nonneoplastic conditions occur in the mediastinum. Imaging plays a central role in the evaluation of mediastinal pathologies and their mimics. Localization of a mediastinal lesion to a compartment and characterization of morphology, density/signal intensity, enhancement, and mass effect on neighboring structures can help narrow the differentials. The International Thymic Malignancy Interest Group (ITMIG) established a cross-sectional imaging-derived and anatomy-based classification system for mediastinal compartments, comprising the prevascular (anterior), visceral (middle), and paravertebral (posterior) compartments. Cross-sectional imaging is integral in the evaluation of mediastinal lesions. Computed tomography (CT) and magnetic resonance imaging (MRI) are useful to characterize mediastinal lesions detected on radiography. Advantages of CT include its widespread availability, fast acquisition time, relatively low cost, and ability to detect calcium. Advantages of MRI include the lack of radiation exposure, superior soft tissue contrast resolution to detect invasion of the mass across tissue planes, including the chest wall and diaphragm, involvement of neurovascular structures, and the potential for dynamic sequences during free-breathing or cinematic cardiac gating to assess motion of the mass relative to adjacent structures. MRI is superior to CT in the differentiation of cystic from solid lesions and in the detection of fat to differentiate thymic hyperplasia from thymic malignancy.

Magnetic resonance imaging for prospective assessment of local recurrence of non-small cell lung cancer after stereotactic body radiation therapy.

OBJECTIVES: To evaluate multi-parametric MRI for distinguishing stereotactic body radiation therapy (SBRT) induced pulmonary fibrosis from local recurrence (LR). MATERIALS AND METHODS: SBRT treated non-small cell lung cancer (NSCLC) patients suspected of LR by conventional imaging underwent MRI: T2 weighted, diffusion weighted imaging, dynamic contrast enhancement (DCE) with a 5-minute delayed sequence. MRI was reported as high or low suspicion of LR. Follow-up imaging ≥12 months or biopsy defined LR status as proven LR, no-LR or not-verified. RESULTS: MRI was performed between 10/2017 and 12/2021, at a median interval of 22.5 (interquartile range 10.5-32.75) months after SBRT. Of the 20 lesions in 18 patients: 4 had proven LR, 10 did not have LR and 6 were not verified for LR due to subsequent additional local and/or systemic therapy. MRI correctly identified as high suspicion LR in all proven LR lesions and low suspicion LR in all confirmed no-LR lesions. All proven LR lesions (4/4) showed heterogeneous enhancement and heterogeneous T2 signal, as compared to the proven no-LR lesions in which 7/10 had homogeneous enhancement and homogeneous T2 signal. DCE kinetic curves could not predict LR status. Although lower apparent diffusion coefficient (ADC) values were seen in proven LR lesions, no absolute cut-off ADC value could determine LR status. CONCLUSION: In this pilot study of NSCLC patients after SBRT, multi-parametric chest MRI was able to correctly determine LR status, with no single parameter being diagnostic by itself. Further studies are warranted.

Imaging Follow-Up of Nonsurgical Therapies for Lung Cancer: AJR Expert Panel Narrative Review.

Lung cancer continues to be the most common cause of cancer-related death worldwide. In the past decade, with the implementation of lung cancer screening programs and advances in surgical and nonsurgical therapies, the survival of patients with lung cancer has increased, as has the number of imaging studies that these patients undergo. However, most patients with lung cancer do not undergo surgical re-section, because they have comorbid disease or lung cancer in an advanced stage at diagnosis. Nonsurgical therapies have continued to evolve with a growing range of systemic and targeted therapies, and there has been an associated evolution in the imaging findings encountered at follow-up examinations after such therapies (e.g., with respect to posttreatment changes, treatment complications, and recurrent tumor). This AJR Expert Panel Narrative Review describes the current status of nonsurgical therapies for lung cancer and their expected and unexpected imaging manifestations. The goal is to provide guidance to radiologists regarding imaging assessment after such therapies, focusing mainly on non-small cell lung cancer. Covered therapies include systemic therapy (conventional chemotherapy, targeted therapy, and immunotherapy), radiotherapy, and thermal ablation.

Imaging of Malignant Pleural, Pericardial, and Peritoneal Mesothelioma.

Malignant mesothelioma is a rare tumor arising from the mesothelial cells that line the pleura, pericardium, peritoneum, and tunica vaginalis. Imaging plays a primary role in the diagnosis, staging, and management of malignant mesothelioma. Multimodality imaging, including radiography, computed tomography (CT), magnetic resonance imaging (MRI), and F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT), is used in a variety of scenarios, including diagnosis, guidance for tissue sampling, staging, and reassessment of disease after therapy. CT is the primary imaging modality used in staging. MRI has superior contrast resolution compared with CT and can add value in terms of determining surgical resectability in equivocal cases. MRI can further assess the degree of local invasion, particularly into the mediastinum, chest wall, and diaphragm, for malignant pleural and pericardial mesotheliomas. FDG PET/CT plays a role in the diagnosis and staging of malignant pleural mesothelioma (MPM) and has been shown to be more accurate than CT, MRI, and PET alone in the staging of malignant pleural mesothelioma. PET/CT can also be used to target lesions for biopsy and to assess prognosis, treatment response, and tumor recurrence.

Liver Injury in Patients With Distal Esophageal Carcinoma After Precision Radiation Therapy: Systematic Review of FDG-PET/CT Patterns.

OBJECTIVE: To determine the incidence and various patterns of radiation-induced liver injury (RILI) and its temporal evolution on fluorodeoxiglucose-positron emission tomography/computed tomography (FDG-PET/CT) after neoadjuvant chemoradiation using precision radiation in patients with esophageal carcinoma. MATERIAL AND METHODS: We evaluated 639 patients with locally advanced esophageal carcinoma who had serial FDG-PET/CTs after neoadjuvant chemoradiation. Two readers reviewed the imaging studies in consensus and recorded the cases where new foci of increased FDG uptake were identified within the radiated liver parenchyma. RILI was confirmed by follow-up imaging or percutaneous biopsy. RESULTS: FDG-avid RILI developed in 39/639 (6%) of patients. The caudate and left hepatic lobe were involved in all cases. There were various patterns of increased FDG uptake: 38% of patients had a single focus of increased FDG uptake and 62% had 2 regions of increased FDG uptake, which were focal nodular or diffuse or a combination of focal nodular and diffuse FDG uptake. On CT, 72% of patients had a poorly-marginated region of low attenuation and 28% had a well-defined region of low attenuation with sharp, well-defined linear borders in the location of the radiation, as confirmed by the treatment plan. CONCLUSION: The caudate and left hepatic lobes were involved in all cases of RILI. The various imaging patterns of RILI on FDG-PET/CT include 1 or 2 regions of increased FDG uptake with a nodular, diffuse, or combined appearance. Awareness of this potential complication of radiation therapy and knowledge of the imaging manifestations of RILI is important to avoid misinterpretation as a metastasis.

Primary thymic neuroblastomas in adults: A clinicopathological and immunohistochemical study of three cases.

Three cases of primary neuroblastomas presenting as anterior mediastinal tumors are presented. The patients are two women and one man between the ages of 57 and 63 year. Clinically, the patients presented with symptoms of chest pain, cough, and shortness of breath. Diagnostic imaging revealed the presence of an anterior mediastina mass. Initial biopsy was non-diagnostic in two patients, while in one patient no biopsy was obtained. Surgical resection via thoracotomy was performed in all three patients. Grossly, the tumors vary in size from 3 to 4.5 cm in greatest dimension, and they were described as well circumscribed but not encapsulated, light brown in color. Areas of hemorrhage and/or necrosis were not described. Histologically, at low power the tumors were surrounded by a rim of adipose tissue containing remnants of thymic tissue with Hassall's corpuscles. At higher magnification, the tumors show the characteristic small round cell proliferation with varying amounts of neurophil. Mitotic activity was present but not in large number. Areas of necrosis and/or hemorrhage were not identified. Immunohistochemically, the tumors show positive staining for NSE, while synaptophysin highlighted neurophil. Other markers epithelial and neuroendocrine were negative. Clinical follow-up information shows that two patients have remained alive 8 and 12 months after initial surgical resection. One patient was lost to follow-up.

Imaging of Immune Checkpoint Inhibitor Immunotherapy for Non-Small Cell Lung Cancer.

The normal immune system identifies and eliminates precancerous and cancerous cells. However, tumors can develop immune resistance mechanisms, one of which involves the exploitation of pathways, termed immune checkpoints, that normally suppress T-cell function. The goal of immune checkpoint inhibitor (ICI) immunotherapy is to boost T-cell-mediated immunity to mount a more effective attack on cancer cells. ICIs have changed the treatment landscape of advanced non-small cell lung cancer (NSCLC), and numerous ICIs have now been approved as first-line treatments for NSCLC by the U.S. Food and Drug Administration. ICIs can cause atypical response patterns such as pseudoprogression, whereby the tumor burden initially increases but then decreases. Therefore, response criteria have been developed specifically for patients receiving immunotherapy. Because ICIs activate the immune system, they can lead to inflammatory side effects, termed immune-related adverse events (irAEs). Usually occurring within weeks to months after the start of therapy, irAEs range from asymptomatic abnormal laboratory results to life-threatening conditions such as encephalitis, pneumonitis, myocarditis, hepatitis, and colitis. It is important to be aware of the imaging appearances of the various irAEs to avoid misinterpreting them as metastatic disease, progressive disease, or infection. The basic principles of ICI therapy; indications for ICI therapy in the setting of NSCLC; response assessment and atypical response patterns of ICI therapy, as compared with conventional chemotherapy; and the spectrum of irAEs seen at imaging are reviewed. An invited commentary by Nishino is available online. ©RSNA, 2022.