Correlative Imaging in a Patient with Cystic Thymoma: CT, MR and PET/CT Comparison

Abstract

SummaryBackgroundCystic thymoma is a rare variant of thymic neoplasm characterized by almost complete cystic degeneration with mixed internal structure. We describe a case of a 60 year-old woman with a cystic thymoma studied with advanced tomographic imaging stydies.CT, MRI and PET/CT with 18F-FDG were performed; volumetric CT and MRI images provided better anatomic evaluation for pre-operative assessment, while PET/CT was helpful for lesion characterization based on 18F-FDG uptake. Although imaging studies are mandatory for pre-operative evaluation of cystic thymoma, final diagnosis still remains surgical.Case ReportA 60-year-old woman with recent chest pain and no history of previous disease was admitted to our departement to investigate the result of a previous chest X-ray that showed bilateral mediastinal enlargement; for this purpose, enhanced chest CT scan was performed using a 64-rows scanner (Toshiba, Aquilion 64, Japan) before and after intravenous bolus administration of iodinated non ionic contrast agent; CT images demonstrated the presence of a large mediastinal mass (11×8 cm) located in the anterior mediastinum who extended from the anonymous vein to the cardio-phrenic space, compressing the left atrium and causing medium lobe atelectasis; bilateral pleural effusion was also present.ConclusionsIn conclusion, correlative imaging plays a foundamental role for the diagnostic evaluation of patient with cystic thymoma. In particular, volumetric CT and MRI studies can provide better anatomic informations regarding internal structure and local tumor spread for pre-operative assessment. Conversely, metabolic imaging using 18F-FDG PET/CT is helpful for lesion characterization differentiating benign from malignant lesion on the basis of intense tracer uptake. The role of PET/MRI is still under investigation. However, final diagnosis still remains surgical even though imaging studies are mandatory for pre-operative patient management.

Relationship Between Computed Tomography Imaging Features and Clinical Characteristics, Masaoka–Koga Stages, and World Health Organization Histological Classifications of Thymoma

“…The infiltration of surrounding fat, pleural nodules, elevated hemidiaphragm, and pulmonary nodules were identified as independent risk factors for patients with myasthenia gravis. These results were similar to those of previous studies (7, 21, 45–48). Klimiec et al (16) suggested that routine CT imaging can effectively identify thymomas; however, radiologists should be cautious in interpreting these images when differentiating between thymic hyperplasia and a normal thymus in patients with myasthenia gravis, as they are not reliable.…”

¹⁸F-FDG PET/BT ile Anterior Mediastinal Kitlelerin Metabolik Karakterizasyonu

“…Complete surgical removal of the thymic tumors with the involved adjacent structures is hence the popular treatment modality ( 11 ). A special subgroup of thymic tumors is the cystic thymus tumor that is characterized by multiple cysts ( 12 ). The 18 F-FDG PET/CT imaging may demonstrate an increased uptake in the cystic thymomas related to the septum or margins of the tumor ( 12 ).…”

“…A special subgroup of thymic tumors is the cystic thymus tumor that is characterized by multiple cysts ( 12 ). The 18 F-FDG PET/CT imaging may demonstrate an increased uptake in the cystic thymomas related to the septum or margins of the tumor ( 12 ). The SUV max cut-off level for malignant and benign thymomas have not been determined, although the previous reports accepted the 4.5-6.3 levels ( 13 ).…”

Quantitative Thoracic Magnetic Resonance Criteria for the Differentiation of Cysts from Solid Masses in the Anterior Mediastinum

“…One aspect worth mentioning is that thymoma may undergo cystic degeneration and show a predominantly cystic appearance (22). There was no cystic thymoma in our population, and our criteria may not work in cystic thymomas.…”