The T2‐FLAIR mismatch sign as an imaging biomarker for oligodendrogliomas in dogs

• Published in: Journal of veterinary internal medicine 2023-07, Vol.37 (4), p.1447-1454
• Main Authors: Garcia‐Mora, Josefa, Parker, Rell L., Cecere, Thomas, Robertson, John L., Rossmeisl, John H.
• Format: Article
• Language: English
• Subjects: Animals; Astrocytoma - genetics; Astrocytoma - veterinary; Biomarkers; Biopsy; Brain cancer; Brain Neoplasms - diagnostic imaging; Brain Neoplasms - veterinary; brain tumor; CNS disorders; Dog Diseases - diagnostic imaging; Dog Diseases - genetics; Dogs; Gene expression; Glioma; Glioma - diagnostic imaging; Glioma - genetics; Glioma - veterinary; Histopathology; Humans; Isocitrate Dehydrogenase - genetics; Magnetic resonance imaging; Magnetic Resonance Imaging - veterinary; Medical prognosis; Mutation; neuroimaging; neurology; Oligodendroglioma - diagnostic imaging; Oligodendroglioma - genetics; Oligodendroglioma - veterinary; oncology‐diagnosis; Quality control; radiology and diagnostic imaging; Retrospective Studies; SMALL ANIMAL; Software; Tumors; Veterinary medicine
• ISSN: 0891-6640; 1939-1676; 1939-1676
• DOI: 10.1111/jvim.16749

Background In humans, the T2‐weighted (T2W)—fluid‐attenuated inversion recovery (FLAIR) mismatch sign (T2FMM) is a specific imaging biomarker for the isocitrate dehydrogenase 1 (IDH1)‐mutated, 1p/19q non‐codeleted low‐grade astrocytomas (LGA). The T2FMM is characterized by a homogeneous hyperintense T2W signal and a hypointense signal with a hyperintense peripheral rim on FLAIR sequences. In gliomas in dogs, the T2FMM has not been described. Hypotheses/Objectives In dogs with focal intra‐axial brain lesions, T2FMM will discriminate gliomas from other lesions. The T2FMM will be associated with the LGA phenotype and presence of microcysts on histopathology. Interobserver agreement for T2FMM magnetic resonance imaging (MRI) features will be high. Animals One hundred eighty‐six dogs with histopathologically diagnosed focal intra‐axial lesions on brain MRI including oligodendrogliomas (n = 90), astrocytomas (n = 47), undefined gliomas (n = 9), cerebrovascular accidents (n = 33), and inflammatory lesions (n = 7). Methods Two blinded raters evaluated the 186 MRI studies and identified cases with the T2FMM. Histopathologic and immunohistochemical slides of T2FMM cases were evaluated for morphologic features and IDH1‐mutations and compared to cases without the T2FMM. Gene expression analyses were performed on a subset of oligodendrogliomas (n = 10) with and without T2FMM. Results The T2FMM was identified in 14/186 (8%) of MRI studies, and all dogs with T2FMM had oligodendrogliomas (n = 12 low‐grade [LGO], n = 2 high‐grade [HGO]; P