T2/FLAIR mismatch sign
Updates to Article Attributes
The T2-FLAIR mismatch sign describes the MRI appearance considered a highly specific radiogenomic signature for diffuse astrocytoma (IDH-mutant, 1p/19q-non-codeleted molecular status), as opposed to other lower-grade gliomas 4,5.
Indeed, a 2021 meta-analysis showed a pooled specificity of 100% for identifying tumours with IDH-mutant, 1p/19q-non-codeleted status, though pooled sensitivity was 42% 6.
It is particularly helpful in distinguishing a diffuse astrocytoma from an oligodendroglioma that will not demonstrate T2-FLAIR mismatch.
Radiographic features
MRI
On T2 weighted images, these tumours have extensive areas of fairly homogeneous and strikingly high signal. On T2-FLAIR, instead, the majority of these areas become relatively hypointense in signal due to incomplete suppression. At the margins of the tumour, a rim of hyperintensity is usually seen.
This appearance is typical of the entity previously known as protoplasmic astrocytoma which is, however, no longer recognised as a distinct entity in the current WHO classification of CNS tumours.
Differential diagnosis
It is important to note that similar signal characteristics can be seen in the bright rim sign of DNET, although almost invariably DNETs are smaller 3.
-<p>The <strong>T2-FLAIR mismatch sign</strong> describes the MRI appearance considered a highly specific radiogenomic signature for <a href="/articles/astrocytic-tumours">diffuse astrocytoma</a> (IDH-mutant, 1p/19q-non-codeleted molecular status), as opposed to other lower-grade gliomas <sup>4,5</sup>. It is particularly helpful in distinguishing a diffuse astrocytoma from an <a href="/articles/oligodendroglioma">oligodendroglioma</a> that will not demonstrate T2-FLAIR mismatch. </p><h4>Radiographic features</h4><h5>MRI</h5><p>On T2 weighted images, these tumours have extensive areas of fairly homogeneous and strikingly high signal. On T2-FLAIR, instead, the majority of these areas become relatively hypointense in signal due to incomplete suppression. At the margins of the tumour, a rim of hyperintensity is usually seen. </p><p>This appearance is typical of the entity previously known as <a href="/articles/protoplasmic-astrocytoma">protoplasmic</a><a href="/articles/protoplasmic-astrocytoma"> astrocytoma</a> which is, however, no longer recognised as a distinct entity in the current <a href="/articles/who-classification-of-cns-tumours-1">WHO classification of CNS tumours</a>.</p><h4>Differential diagnosis</h4><p>It is important to note that similar signal characteristics can be seen in the <a href="/articles/bright-rim-sign-dnet-1">bright rim sign</a> of <a href="/articles/dysembryoplastic-neuroepithelial-tumour">DNET</a>, although almost invariably DNETs are smaller <sup>3</sup>.</p>- +<p>The <strong>T2-FLAIR mismatch sign</strong> describes the MRI appearance considered a highly specific radiogenomic signature for <a href="/articles/astrocytic-tumours">diffuse astrocytoma</a> (IDH-mutant, 1p/19q-non-codeleted molecular status), as opposed to other lower-grade gliomas <sup>4,5</sup>.</p><p>Indeed, a 2021 meta-analysis showed a pooled specificity of 100% for identifying tumours with IDH-mutant, 1p/19q-non-codeleted status, though pooled sensitivity was 42% <sup>6</sup>.</p><p>It is particularly helpful in distinguishing a diffuse astrocytoma from an <a href="/articles/oligodendroglioma">oligodendroglioma</a> that will not demonstrate T2-FLAIR mismatch. </p><h4>Radiographic features</h4><h5>MRI</h5><p>On T2 weighted images, these tumours have extensive areas of fairly homogeneous and strikingly high signal. On T2-FLAIR, instead, the majority of these areas become relatively hypointense in signal due to incomplete suppression. At the margins of the tumour, a rim of hyperintensity is usually seen. </p><p>This appearance is typical of the entity previously known as <a href="/articles/protoplasmic-astrocytoma">protoplasmic</a><a href="/articles/protoplasmic-astrocytoma"> astrocytoma</a> which is, however, no longer recognised as a distinct entity in the current <a href="/articles/who-classification-of-cns-tumours-1">WHO classification of CNS tumours</a>.</p><h4>Differential diagnosis</h4><p>It is important to note that similar signal characteristics can be seen in the <a href="/articles/bright-rim-sign-dnet-1">bright rim sign</a> of <a href="/articles/dysembryoplastic-neuroepithelial-tumour">DNET</a>, although almost invariably DNETs are smaller <sup>3</sup>.</p>
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