[18F]FDG positron emission tomography/computed tomography and multidetector computed tomography roles in thymic lesion treatment planning. 
Thymic masses may represent an unsolved diagnostic problem which often require surgical procedures for an accurate staging.  A non-invasive way to determine the nature of thymic lesions would help identify the patients which are true candidates for surgery.  Our retrospective study aims to assess multidetector computed tomography and 2-[(18)F]fluoro-2-deoxyglucose positron emission tomography/computed tomography ([(18)F]FDG-PET/CT) capacity to distinguish benign from malignant thymic lesions.  Helical multidetector CT (MDCT) and [(18)F]FDG-PET/CT of twenty consecutive patients presenting with a thymic mass at our Institute were retrospectively analyzed.  MDCT scans were focused on morphologic features and invasiveness characteristics.  Qualitative and semi-quantitative analyses by maximum standardized uptake value corrected for body weight (SUVbw max) were performed on [(18)F]FDG-PET/CT.  In all cases, readers were blinded to pathology findings.  Both imaging techniques were correlated to final pathology.  Student's t-test was performed on SUVbw max stratified for thymic epithelial tumors.  In the group of benign lesions MDCT correctly identified well-defined margins of masses in 8 out of 8 patients whereas [(18)F]FDG-PET/CT was negative in 7 out of 8 patients.  Among malignant lesions MDCT revealed mediastinum fat or infiltration of adjacent organs in 10/12 patients.  On the other hand [(18)F]FDG-PET/CT showed increased radiotracer uptake in 12/12 patients.  MDCT and [(18)F]FDG-PET/CT alone are not able to differentiate the nature of thymic lesions.  However, they are two non-invasive complementary techniques which can be used to differentiate benign from high-risk malignant thymic lesions.  These findings should be taken into account before surgery is performed as a diagnostic procedure.