Molecular & Genetic Markers
1p/19q codeletion
1p/19q codeletion is the loss of segments of chromosomes 1 and 19 that, with an IDH mutation, defines oligodendroglioma and predicts a favorable treatment response.
In short: 1p/19q codeletion
- It is the combined loss of parts of chromosomes 1 and 19.
- With an IDH mutation, it defines oligodendroglioma.
- It predicts a favorable response to treatment.
- It is a key test in classifying diffuse gliomas.
What it is
1p/19q codeletion is the simultaneous loss of the short arm of chromosome 1 (1p) and the long arm of chromosome 19 (19q) in tumor cells. In a diffuse glioma that also has an IDH mutation, the presence of 1p/19q codeletion defines the tumor as an oligodendroglioma and predicts a favorable response to treatment.
Understanding 1p/19q codeletion
Among IDH-mutant diffuse gliomas, the 1p/19q status separates the two types: tumors with 1p/19q codeletion are oligodendrogliomas, while those without it are astrocytomas. This distinction matters because oligodendrogliomas (1p/19q-codeleted) generally have the best outlook among adult diffuse gliomas and respond particularly well to chemotherapy (such as the PCV regimen). The codeletion is detected by molecular testing on the tumor tissue. Because it is required to diagnose oligodendroglioma and predicts treatment response, 1p/19q testing is a standard part of evaluating IDH-mutant diffuse gliomas. Understanding 1p/19q codeletion clarifies the molecular feature that defines oligodendroglioma and signals a favorable treatment response.
Why it matters
Understanding 1p/19q codeletion helps patients and families see why this test matters — combined with an IDH mutation, it defines oligodendroglioma, the most favorable adult diffuse glioma, and predicts a good response to chemotherapy.
Common questions
What is 1p/19q codeletion?
The combined loss of parts of chromosomes 1 and 19.
What does it define?
With an IDH mutation, it defines oligodendroglioma.
What does it predict?
A favorable response to treatment, including chemotherapy.
Bottom line
1p/19q codeletion is the loss of parts of chromosomes 1 and 19 that, with an IDH mutation, defines oligodendroglioma and predicts a favorable treatment response.
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