1p/19q co-deletion
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1p19q codeletion stands for the combined loss of the short arm chromosome 1 (i.e. 1p) and the long arm of chromosome 19 (i.e. 19q) and is recognized as a genetic marker predictive of therapeutic response to both chemotherapy and combined chemoradiotherapy and overall longer survival in patients with diffuse gliomas, especially those with oligodendroglial components
IDH positive + 1p/19q co-deletion = oligodendroglioma = better prognosis
IDH positive + no 1p/19q co-deletion = astrocytoma 1)
Indications
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Currently, classification of neoplasms, especially regarding gliomas, is established on molecular mutations in isocitrate dehydrogenase (IDH) genes and the presence of 1p/19q co-deletion 2)
1p/19q co-deletion should be tested whenever oligodendroglial features are present or if oligodendroglioma is suspected on other grounds. This is tested using FISH (fluorescence in situ hybridization) or PCR. It is often sent out, results typically take 3–7 days. Cost for FISH is on the order of $200 U.S., PCR is $300–500 U.S
Oligodendrocyte transcriptional factor-2 (Olig2) is an essential marker for oligodendrocytes expression. Olig2 marker cannot be used as an alternative diagnostic method for 1p 19q co-deletion to distinguish oligodendrogliomas from other glial neoplasms. Although some glial tumors showed diffuse Olig2 expression, 1p19q co-deletion testing is the best diagnostic method 3).
Oligodendroglioma 1p/19q co-deletion
Anaplastic astrocytoma without 1p/19q co-deletion
Extraventricular neurocytoma
1p/19q co-deletion has not been reported in central neurocytoma, but it can be seen in extraventricular neurocytoma.