Computed tomography and magnetic resonance imaging of mediastinal tumors

Abstract

We describe the clinical, pathological, and imaging findings of mediastinal tumors with focus on thymic hyperplasia, thymic epithelial tumors, and germ cell tumors, malignant lymphoma, and various cystic masses. Chemical shift magnetic resonance imaging (MRI) is useful in characterization of the normal thymus and differentiation of hyperplastic thymus and thymic tumors. In contrast to noninvasive thymomas, invasive thymomas and thymic carcinomas show a more aggressive growth pattern. Local invasion and pleural spread are characteristic of invasive thymoma and mediastinal lymphadenopathy and distant metastasis suggest thymic carcinomas. Mature teratoma typically shows various computed tomography (CT) attenuation, and MR signal intensity depending on its contents and fat tissue and bone within the lesions are its characteristic findings. Seminomas typically have homogenous internal CT attenuation and MR signal intensity with minimal contrast enhancement. Nonseminomatous malignant germ cell tumors characteristically show prominent internal degenerative changes and invasion to the adjacent structures. In mediastinal lymphomas, a residual mass is common after treatment and MRI provides important information in distinguishing viable tumors from residual benign masses. Some mediastinal cysts may reveal high attenuation similar to solid lesions on CT depending on their contents and MRI can be useful in the differentiation of cystic masses from solid lesions.

Positron Emission Tomography/Computed Tomography in Mediastinal Masses

“…RTH histolojik veya radyolojik görünümlerinde değişiklik olmadan timus volümünün artmasıdır. RTH kemoterapi tamamlandıktan sonra, çocuklarda ortalama 6. ayda, erişkinlerde ortalama 9. ayda görülür (28). Maalesef normal timus tutulumu, RTH, lenfoma ve rekürren hastalığı SUV maks değerlerine bakarak ayırt etmek mümkün değildir.…”

“…Genç erişkinler en sık hasta grubudur. Benign GHT'ler kadın ve erkeklerde aynı oranda görülürken; malign GHT'lerin %90'ı erkeklerde görülür (28,37,38). Mediastinal GHT'ler histolojik olarak gonadal germ hücrelerin tüm tiplerini içerebilirler.…”

Management of large mediastinal masses: surgical and anesthesiological considerations

“…Traditionally, following chest radiography, computed tomography (CT) of the chest is the initial choice of imaging modality in the evaluation of mediastinal masses (6). It is valuable in demonstrating the morphology of the tumor, its exact anatomical location, and its relation with structures in the mediastinum.…”

Imaging the posterior mediastinum: a multimodality approach

“…On CT, enlarged lymph nodes usually have homogeneous soft-tissue attenuation with mild-to-moderate contrast enhancement. If large, however, they can show cystic or necrotic changes (54). CT can depict the anatomic extent of disease and also allow an evaluation of abdominal lymph nodes (8).…”

“…If performed, lymphoma appears as one or more, relatively homogeneous masses with low signal intensity on T1-weighted images and intermediate-to-high signal on T2-weighted images (3). MRI can also evaluate treatment response after chemotherapy, showing inactive residual fibrotic masses as homogeneous, hypointense, and nonenhancing lesions (54). To obtain a global evaluation, 18 F-FDG-PET scanning is recommended 6-8 weeks after treatment in patients with Hodgkin's lymphoma and diffuse large B-cell lymphoma, which are FDG-avid and potentially curable (55).…”