Usefulness of [11C]methionine PET in the diagnosis of dysembryoplastic neuroepithelial tumor with temporal lobe epilepsy

Purpose: We assessed the diagnostic value of [C-11]methionine (MET) positron emission tomography (PET) in the differential diagnosis of dysembryoplastic neuroepithelial tumors (DNETs) among benign tumors associated with temporal lobe epilepsy (TLE). Methods: This series consisted of seven TLE patients with benign tumors in the temporal lobe. After MET-PET study, all seven patients underwent tumor resection along with focus excision. The uptake of tracers was evaluated by the lesion-to-contralateral ratio (L/C ratio) and the standardized uptake value (SUV). We also assessed the relation between MET uptake and proliferation capacity observed in the surgical specimens. Results: Whereas four patients with DNETs did not show high MET uptake visually, the ganglioglioma and gliomas of the remaining three patients were identified as high-MET-uptake lesions. In the DNETs, the SUV ranged from 1.03 to 1.41, and the L/C ratio ranged from 0.99 to 1.14. MET uptake was significantly lower in the patients with DNETs than in the patients with ganglioglioma and brain gliomas (SUV, p=0.045; L/C ratio, p=0.0079). The Ki-67 labeling index was 4% in one patient with DNET and 5% in one patient with pleomorphic xanthoastrocytoma (higher labeling index). The higher labeling index was not related to high MET uptake based on the SUV (p=0.91) and L/C ratio (p=0.38). Conclusions: Negative MET uptake in benign temporal lobe tumors with TLE is consistent with a preoperative diagnosis of DNET.