FDG-PET/CT has become the standard for staging and assessment of treatment response for lymphomas that are FDG-PET-avid at baseline or at the time recurrence [91-97]. A caveat is that although a negative surveillance FDG-PET/CT is reassuring of a good outcome, a positive FDG-PET/CT can be misleading, as it does not always implicate residual or recurrent lymphoma [96,98]. CT and MRI can be used for surveillance of lymphadenopathy when the metabolic activity of the lymphadenopathy is not of interest and when allowed within a clinical protocol. With regard to prevascular mediastinal masses, a negative FDG-PET/CT has been shown to be helpful in excluding malignancy; however, a positive FDG-PET/CT has little value for discrimination between benign and malignant lesions [53]. The frequent FDG-PET/CT avidity of normal and hyperplastic thymus [54] is a confounder in FDG-PET/CT assessment of the prevascular mediastinum. Benign thymic cysts can also be FDG-PET/CT-avid [42]. Combined use of FDG-PET/CT and DCE MRI has been shown to be helpful to distinguish prevascular mediastinal solid tumors from one another [55]. Higher SUVs on FDG-PET/CT are more frequently found in high-risk thymoma, thymic carcinoma, and lymphoma than in low-risk thymoma [55-57]. FDG-PET/CT appears to be more sensitive than CT alone for detection of mediastinal recurrence of thymoma [99]. Cross-sectional imaging by MRI remains superior to CT for detection of invasion of the mass across tissue planes, including the chest wall and diaphragm, and involvement of neurovascular structures, secondary to its higher soft- Imaging of Mediastinal Masses tissue contrast [48-52].
Imaging of Mediastinal Masses. FDG-PET/CT has become the standard for staging and assessment of treatment response for lymphomas that are FDG-PET-avid at baseline or at the time recurrence [91-97]. A caveat is that although a negative surveillance FDG-PET/CT is reassuring of a good outcome, a positive FDG-PET/CT can be misleading, as it does not always implicate residual or recurrent lymphoma [96,98]. CT and MRI can be used for surveillance of lymphadenopathy when the metabolic activity of the lymphadenopathy is not of interest and when allowed within a clinical protocol. With regard to prevascular mediastinal masses, a negative FDG-PET/CT has been shown to be helpful in excluding malignancy; however, a positive FDG-PET/CT has little value for discrimination between benign and malignant lesions [53]. The frequent FDG-PET/CT avidity of normal and hyperplastic thymus [54] is a confounder in FDG-PET/CT assessment of the prevascular mediastinum. Benign thymic cysts can also be FDG-PET/CT-avid [42]. Combined use of FDG-PET/CT and DCE MRI has been shown to be helpful to distinguish prevascular mediastinal solid tumors from one another [55]. Higher SUVs on FDG-PET/CT are more frequently found in high-risk thymoma, thymic carcinoma, and lymphoma than in low-risk thymoma [55-57]. FDG-PET/CT appears to be more sensitive than CT alone for detection of mediastinal recurrence of thymoma [99]. Cross-sectional imaging by MRI remains superior to CT for detection of invasion of the mass across tissue planes, including the chest wall and diaphragm, and involvement of neurovascular structures, secondary to its higher soft- Imaging of Mediastinal Masses tissue contrast [48-52].