Abstract
T2-FLAIR mismatch sign is known as a highly specific imaging marker of IDH-mutant astrocytomas. This study was intended to clarify what the T2-FLAIR mismatch sign represents by pathological analysis of lower-grade gliomas rediagnosed in accordance with the WHO 2016 classification. We retrospectively analyzed the records of 64 patients diagnosed with WHO grade II and III diffuse gliomas between June 2009 and November 2018. T2-FLAIR mismatch sign was found in 10 (45%) out of 22 patients with IDH-mutant astrocytoma, 1 (5%) out of 20 with oligodendroglioma, and 1 (5%) out of 22 with IDH-wild-type astrocytoma. T2-FLAIR mismatch sign as a marker of IDH-mutant astrocytomas showed positive predictive value of 83%. Among 22 patients with IDH-mutant astrocytomas, microcystic change was found in eight, of which seven showed T2-FLAIR mismatch sign. Microcystic change was significantly associated with T2-FLAIR mismatch sign (P < 0.01). From multi-sampling in a patient, abundant microcysts were observed upon HE staining of specimens from the T2-FLAIR mismatched region, while microcysts were hardly observed from the T2-FLAIR matched one. All three protoplasmic astrocytomas among our IDH-mutant astrocytomas presented T2-FLAIR mismatch sign. In conclusion, T2-FLAIR mismatch sign may reflect microcyst formation in IDH-mutant astrocytomas and be common in IDH-mutant protoplasmic astrocytoma.
Highlights
Diffuse lower-grade gliomas are diagnosed by histopathological and molecular features, such as isocitrate dehydrogenase (IDH) 1 and 2 gene mutation and codeletion of chromosomes 1p and 19q (1p19q codeletion) in the World Health Organization (WHO) 2016 classification[1,2]
T2-FLAIR mismatch sign, which is defined as the presence of complete/near-complete hyperintense signals on a T2-weighted image and a relatively hypointense signal on FLAIR except for a hyperintense peripheral rim, has been suggested[7] and validated as a highly specific imaging marker of IDH-mutant astrocytomas, with specificity as high as 100%8
We analyzed 64 patients with lower-grade gliomas who were rediagnosed in accordance with the WHO 2016 classification (Table 1)
Summary
Diffuse lower-grade gliomas are diagnosed by histopathological and molecular features, such as isocitrate dehydrogenase (IDH) 1 and 2 gene mutation and codeletion of chromosomes 1p and 19q (1p19q codeletion) in the World Health Organization (WHO) 2016 classification[1,2]. Oligodendrogliomas harbor both IDH mutation and 1p19q codeletion. IDH-wild-type astrocytomas show a worse clinical outcome than gliomas with IDH mutation[5,6]. The purpose of this study is to clarify what the T2-FLAIR mismatch sign represents by pathological analysis of lower-grade gliomas rediagnosed in accordance with the WHO 2016 classification
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