Clinicopathological analysis of T2-FLAIR mismatch sign in lower-grade gliomas

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.

Figure 1

An example of T2-FLAIR mismatch sign. A patient with IDH-mutant astrocytoma in the right frontal lobe. Left shows T2-weighted image and right shows FLAIR image.

Figure 2

Multi-sampling in a patient with IDH-mutant astrocytoma. (A) MR imaging. Left shows T2-weighted image and right shows FLAIR image. Red circles show T2-FLAIR matched and mismatched regions. (B) Hematoxylin–eosin (HE)-stained sections. Left shows HE staining of specimens from the T2-FLAIR mismatched region, where multiple microcysts were observed. Right shows HE staining of specimens from the T2-FLAIR matched region, where microcysts were hardly observed.

Figure 3

Kaplan–Meier curves of progression-free survival (PFS) and overall survival (OS). (A) Kaplan–Meier curves of PFS in IDH-mutant astrocytomas comparing the presence of T2-FLAIR mismatch sign (red line) with its absence (black line). (B) Kaplan–Meier curves of OS in IDH-mutant astrocytomas comparing the presence of T2-FLAIR mismatch sign (red line) with its absence (black line).