[18F]FDG positron emission tomography/computed tomography and multidetector computed tomography roles in thymic lesion treatment planning.
BACKGROUND
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Travaini
Laura L
LL
Division of Nuclear Medicine, European Institute of Oncology, 20141 Milan, Italy.
Petralia
Giuseppe
G
Trifirò
Giuseppe
G
Ravasi
Laura
L
Galetta
Domenico
D
Carbone
Giuseppe
G
Falcini
Fabio
F
Spaggiari
Lorenzo
L
Bellomi
Massimo
M
Paganelli
Giovanni
G
D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012189:Retrospective Studies; D013953:Thymus Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D036542:Tomography, Spiral Computed / Q000379:methods*
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18