Mediastinum (Hong Kong, China)最新文献

Esophageal duplication represents one of the most common types of bronchopulmonary foregut malformations. These rare congenital anomalies occur secondary to embryological aberrations between the 4th and 8th weeks of gestation. In order to be classified as an esophageal cyst a mediastinal cyst must have a close proximity with the esophagus, be lined by alimentary (squamous epithelium) or tracheobronchial mucosa and covered by two smooth muscle layers. These rare anomalies are often asymptomatic during adulthood. However, they can cause symptoms in early childhood, generally during the first 2 years of life. Variations in location, size, presence or absence of heterotopic mucosa, will dictate the clinical presentation. Dysphagia, food impaction, persistent cough and chest pain are common clinical presentations. Imaging studies including esophagram, computed tomography (CT) and magnetic resonance imaging (MRI) can provide key findings to reach the diagnosis. Nonetheless, endoscopic evaluation, particularly endoscopic ultrasound (EUS) is the most valuable tool to determine whether this lesion is cystic versus solid and or if there are abnormal mucosal findings. Needle biopsies are controversial but can help with drainage and to rule out malignant transformation. Therapeutic options include endoluminal drainage. However, more definitive therapies include surgical excision. Open and minimally invasive (laparoscopic and thoracoscopic) techniques have been demonstrated to be safe and effective at completely removing these lesions. Recently, robotic-assisted resections have gained more attention with case reports and series reporting excellent outcomes.

Background: The propensity of thymic cysts to mimic solid thymic epithelial tumors (TETs) on computed tomography (CT), on account of attenuation values greater than water and thickened or calcified walls, can lead to non-therapeutic thymectomy. These lesions can fluctuate in volume, CT attenuation, and magnetic resonance imaging (MRI) signal over time. We hypothesized that spontaneous hemorrhage and resorption may contribute to their variable appearance over time.

Methods: Completely excised thymic cysts were identified retrospectively over a 20-year period by their pathologic diagnosis. Cysts were excluded if they did not have available presurgical imaging, were not prevascular, were located within or contained an enhancing mass by imaging, or were of non-thymic origin upon microscopic review. Histopathological analysis of all available resected thymic cyst material and radiologic analysis of the cysts on pre-operative imaging were performed.

Results: Upon application of exclusion criteria, we identified 18 thymic cysts from the initial 85 mediastinal cystic specimens. Most cysts were unilocular (11/15, 73%), showed turbid-to-semisolid, hemorrhagic fluid (10/12, 83%) and showed histopathological findings suggestive of intralesional microbleeding (14/18, 78%), remodeling (8/18, 44%), pathological wound healing/scarring of the capsule (16/18, 89%), and fat necrosis in the surrounding thymic tissue (12/18, 67%). On CT, 6/17 (35%) cysts demonstrated wall calcification. Sixty-five percent (11/17) had attenuation values ≥20 Hounsfield units (HU). Two of the 4 cysts imaged by MRI were T1-isointense, one was mixed hyper- and isointense, and one T1-hypointense to muscle, with iso- and hyperintensity indicating hemorrhagic or proteinaceous content. Twenty-five percent (1/4) of cyst walls imaged by MRI were T1/T2-hypointense, indicating presence of calcification, hemosiderin, and/or fibrosis.

Conclusions: Resected thymic cysts in this cohort often showed features suggestive of intralesional microbleeding, inflammation, and fibrosis, which may explain their appearance and behavior over time on CT and MRI.

Background: The International Thymic Malignancy Interest Group (ITMIG) proposed an internationally accepted division of the mediastinum into three compartments based on computed tomography (CT): anterior (prevascular), middle (visceral) and posterior (paravertebral) compartment. There is no generally accepted definition for the term "giant" when applied to middle mediastinal lesions. We defined the term "giant" and described our surgical experience in treating patients with giant lesions of the middle mediastinum.

Methods: CT imaging of patients operated in our center from January 2016 to August 2021 for mediastinal lesions was reviewed. Lesions were categorized to one of the ITMIG-defined compartments. Lesion size at diagnosis was measured at its largest diameter on axial CT imaging. Giant middle mediastinal lesions were defined as lesions having a size ≥90^th percentile of our middle mediastinal lesion cohort. Patients with giant middle mediastinal lesions were further analyzed.

Results: Thirty-six patients (23%) had lesions located in the middle mediastinal compartment. Most common diagnoses were mediastinal cysts (n=10, 28%), metastatic lesions (n=6, 17%), lymphomas (n=5, 14%), and sarcomas (n=3, 8%). Ninetieth percentile lesion size was 73 mm. As per definition, four patients had giant middle mediastinal lesions. All these four lesions were of mesenchymal origin including oesophageal leiomyoma, synovial sarcoma, leiomyosarcoma and undifferentiated round cell sarcoma. Resection was performed through posterolateral thoracotomy or sternotomy, with or without cardiopulmonary bypass.

Conclusions: The term "giant" could be defined as a mass larger or equal to 73 mm. This definition selected specifically lesions with mesenchymal origin and may therefore guide diagnostic algorithm and patient management.

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 8^th 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.

Cystic mediastinal masses have traditionally represented a diagnostic dilemma with differentiation of malignant masses a particular area of concern. Each imaging modality has strengths and weaknesses in mediastinal imaging-computed tomography (CT) offers increased spatial resolution at the cost of poorer soft tissue differentiation and requiring ionizing radiation, while magnetic resonance imaging (MRI) offers superior soft tissue contrast/characterization at significantly greater cost. Ultrasound offers real-time visualization but is operator and tissue dependent. [18F]fluoro-D-glucose (F-18 FDG) positron emission tomography (F-18 FDG PET) CT provides functional information, but poorer spatial resolution. Recent advances have focused upon the use of magnetic resonance imaging to aid in characterization of cystic mediastinal lesions, particularly in the context of indeterminate CT findings. The mediastinum may be divided into three anatomic compartments: prevascular, visceral, and paravertebral. All three compartments extend superiorly from the thoracic inlet and inferiorly to the diaphragm. These compartments provide a useful framework for categorizing normal and pathologic mediastinal processes. In this article, we will review the imaging characteristics of mediastinal cystic lesions via a case-based review divided by anatomical mediastinal compartments. Characteristic imaging features and troubleshooting are particular areas of focus. Normal variants that may mimic cystic pathology are discussed. The roles of CT and MRI will be emphasized. Cases from our institution are presented as illustrative examples.