Question 810
{"accessible":false,"alternatives":[{"id":4097,"text":"additional tests are required"},{"id":4098,"text":"astrocytoma grade 4 IDH mutant"},{"id":4099,"text":"astrocytoma grade 4 IDH wild-type"},{"id":4100,"text":"glioblastoma IDH mutant"},{"id":4101,"text":"glioblastoma IDH wild-type"}],"archived":false,"correctAlternativeId":4097,"explanation":"\u003cp\u003eThis is almost a trick question.\u003c/p\u003e\u003cp\u003eThe presence of necrosis in an astrocytic tumour is sufficient to make it a grade 4 tumour.\u0026nbsp;\u003c/p\u003e\u003cp\u003eThe issue is with IDH status. Although IDH1 R132H is the most common, but by no means the only IDH mutation, in this age group, there is a reasonable chance (5-10%) that they harbour a non-IDH1 R132H mutation and before the tumour can be adequately classified according to the 2021\u0026nbsp;\u003ca href=\"/articles/who-classification-of-cns-tumours-1\"\u003eWHO classification\u0026nbsp;of CNS tumours\u003c/a\u003e IDH needs to be sequenced to exclude an alternative IDH1 or IDH2 mutation.\u0026nbsp;\u003c/p\u003e\u003cp\u003eNote, if this tumour was shown to have a non R132H IDH mutation, it would be an astrocytoma grade 4, whereas if it was IDH-wildtype it would be a glioblastoma.\u0026nbsp;\u003c/p\u003e","id":810,"imageUrl":null,"imageAttribution":null,"imageAttributionCaseInfo":null,"firstQuestionPath":"/questions/2841","nextQuestionPath":"/articles/isocitrate-dehydrogenase-idh-1/questions/658","relatedArticles":[{"id":4910,"title":"Glioblastoma, IDH-wildtype","link":"/articles/glioblastoma-idh-wildtype?lang=gb"}],"alsoUsedIn":[],"stem":"\u003cp\u003eA 40-year-old male, with no prior history of a brain tumour, undergoes resection of a heterogeneous left frontal lobe tumour. Histology demonstrates an astrocytic tumour with necrosis and microvascular proliferation. Immunohistochemistry confirms astrocytic differentiation and is negative for IDH1 R132H mutations. How should this tumour be classified?\u003c/p\u003e","menuLinks":[{"text":"Report problem with question","url":"https://docs.google.com/forms/d/e/1FAIpQLSfO3soWYhOjJ7yErSysyCe5V4A1CqW7WK3rDA7MtAkecMGqNw/viewform?entry.1624461248\u0026entry.553583435=https://radiopaedia.org/questions/810"}],"attemptsPercentages":[{"alternativeId":"4099","percentage":17},{"alternativeId":"4101","percentage":36},{"alternativeId":"4100","percentage":11},{"alternativeId":"4098","percentage":7},{"alternativeId":"4097","percentage":28}],"promptToLogin":false,"questionManager":false,"articleId":"isocitrate-dehydrogenase-idh"}