Thymic lesions and myasthenia gravis. Diagnosis based on mediastinal imaging and pathological findings.
OBJECTIVE
To achieve a better understanding of the role of CT and MR imaging in the study of the mediastinum in patients with myasthenia gravis (MG).


METHODS
Mediastinal CT and MR findings were correlated with the histopathological results in 104 thymectomized MG patients.


RESULTS
CT was performed in 104 patients; in 11 of them, MR was also carried out. 44 patients had hyperplasia at histology. On CT, thymic hyperplasia was confirmed in 16 cases, thymoma was diagnosed in 10 and a normal thymus in 18 (sensitivity 36%, specificity 95%). Of 52 patients with thymoma at histology, CT showed thymoma in 46, hyperplasia in 1, and normal thymus in 5. CT showed 88.5% sensitivity and 77% specificity for thymoma. In 10 patients with invasive thymoma, CT was indiscriminate, while invasiveness was detected in 7 cases at MR (70% sensitivity) and at CT in 1 case. Both CT and MR detected tumor recurrence in 5 cases, but the exact localization and degree of invasion were best defined by MR.


CONCLUSIONS
In MG patients CT is a sensitive, specific and efficient modality for detecting thymoma, but is less so for detecting thymic hyperplasia. MR was shown to be accurate in detecting invasive thymoma both preoperatively and in postoperative follow-up.
Pirronti
T
T
Institutes of Radiology and Neurology, Catholic University, Rome, Italy.
Rinaldi
P
P
Batocchi
A P
AP
Evoli
A
A
Di Schino
C
C
Marano
P
P
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007472:Iohexol / Q000031:analogs & derivatives*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000175:diagnosis* / Q000000981:diagnostic imaging; D012680:Sensitivity and Specificity; D013950:Thymus Gland / Q000473:pathology*; D013952:Thymus Hyperplasia / Q000175:diagnosis* / Q000000981:diagnostic imaging; D013953:Thymus Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed
D003287:Contrast Media; D007472:Iohexol; C038192:iopromide; D019786:Gadolinium DTPA