T2-FLAIR mismatch sign in dysembryoplasticneuroepithelial tumor

Purpose: T2-FLAIR mismatch sign was reported as specific imaging marker in non-enhancing diffuse astrocytoma, IDH-mutant & 1p/19q non-codeleted. However, most of the previous studies for T2-FLAIR mismatch sign were confirmed only among lower grade glioma. The aim of this study is to assess the T2-FLAIR mismatch sign in dysembryoplastic neuroepithelial tumor (DNET) and unveil the exception rules of the sign. Method: Eleven patients with histopathologically confirmed DNET were included in this study. The MR images were evaluated by 2 independent reviewers to assess (i) the presence or absence of T2-FLAIR mismatch sign and (ii) the presence or absence of gadolinium enhancement. CT was also performed to evaluate calcification and localized thinning of the skull bone. Inter-reviewer agreement with Cohen's kappa (kappa) was calculated. Results: The T2-FLAIR mismatch sign was present in 8 cases (72.7 %) and absent in 3 cases (27.3 %). None of them showed contrast enhancement on initial MR images. The inter-reviewer agreement for T2-FLAIR mismatch and CT characteristics was excellent (kappa( )= 1.00). All of the DNET without T2-FLAIR mismatch presented with calcification on CT. All of the DNET adjacent to skull vault (5 cases) presented with localized bone thinning overlying the tumor. Conclusions: The T2-FLAIR mismatch sign was observed in more than half of the DNET and the sign is not specific for diffuse astrocytoma, IDH-mutant & 1p19q non-codeleted. The localized skull bone thinning overlying the tumor might help for diagnosis of DNET in some cases.